# Leap year

Leap year
You are encouraged to solve this task according to the task description, using any language you may know.

Determine whether a given year is a leap year in the Gregorian calendar.

## 11l

Translation of: Python

<lang 11l>F is_leap_year(year)

```  I year % 100 == 0
R year % 400 == 0
R year % 4 == 0</lang>
```

## 360 Assembly

This is a callable subroutine to determine whether or not a given zoned-decimal 4-digit year is a Leap Year. Leap years are "evenly divisible" by 4, except those which end in '00' and are not evenly divisible by 400. The subroutine receives two parameters:

``` (1) a 4-digit year (CCYY)
(2) an 8-byte work area
```

The value returned in Register 15 (by convention the "return code") indicates whether the year is a Leap Year:

``` When R15 = zero, the year is a leap year.
Otherwise it is not.
```

<lang 360 Assembly> LPCK CSECT

```    USING LPCK,15
STM  0,12,20(13)   STORE CALLER REGS
LM   1,2,0(1)      R1 -> CCYY, R2 -> DOUBLE-WORD WORK AREA
PACK 0(8,2),0(4,1) PACK CCYY INTO WORK AREA
CVB  0,0(2)        CONVERT TO BINARY (R0 = CCYY)
SRDL 0,32          R0|R1 = CCYY
LA   2,100         R2 = 100
DR   0,2           DIVIDE CCYY BY 100: R0 = YY, R1 = CC
LTR  0,0           YY = 0? IF CCYY DIV BY 100, LY IFF DIV BY 400
BZ   A               YES: R0|R1 = CC; CCYY DIV BY 100, TEST CC
SRDL 0,32            NO: R0|R1 = YY; CCYY NOT DIV BY 100, TEST YY
```

A LA 2,4 DIVISOR = 4; DIVIDEND = YY, OR DIV BY 100 CC

```    DR   0,2           DIVIDE BY 4: R0 = REMAINDER, R1 = QUOTIENT
LR   15,0          LOAD REMAINDER: IF 0, THEN LEAP YEAR
LM   0,12,20(13)   RESTORE REGS
BR   14
END
```

</lang>

Sample invocation from a COBOL program:

WORKING-STORAGE SECTION. 01 FILLER.

```   05 YEAR-VALUE PIC 9(4).
05 WKAREA PIC X(8).
```

PROCEDURE DIVISION.

```   MOVE 1936 TO YEAR-VALUE
CALL 'LPCK' USING YEAR-VALUE, WKAREA
PERFORM RESULT-DISPLAY
MOVE 1900 TO YEAR-VALUE
CALL 'LPCK' USING YEAR-VALUE, WKAREA
PERFORM RESULT-DISPLAY
GOBACK.
```

RESULT-DISPLAY.

```   IF RETURN-CODE = ZERO DISPLAY YEAR-VALUE ' IS A LEAP YEAR'
ELSE DISPLAY YEAR-VALUE ' IS NOT A LEAP YEAR'.
```

## 68000 Assembly

<lang 68000 Assembly>;Example

```       move.l  #2018,d0
bsr     leap_year
addi.l  #28,d1      ; # days in February 2018
rts
```
Leap Year
Input
d0=year
Output
d1=1 if leap year, 0 if not leap year
zero flag clear if leap year, set if not

leap_year:

```       cmpi.l  #1752,d0
ble.s   not_leap_year
```
```       move.l  d0,d1
lsr.l   #1,d1
bcs.s   not_leap_year
lsr.l   #1,d1
bcs.s   not_leap_year
```
If we got here, year is divisible by 4.
```       move.l  d0,d1
divu    #100,d1
swap    d1
tst.w   d1
bne.s   is_leap_year
```
If we got here, year is divisible by 100.
```       move.l  d0,d1
divu    #400,d1
swap    d1
tst.w   d1
bne.s   not_leap_year
```

is_leap_year:

```       moveq.l #1,d1
rts
```

not_leap_year:

```       moveq.l #0,d1
rts
```

</lang>

## 8080 Assembly

<lang 8080asm> org 100h jmp test ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; Check if a year is a leap year. ;; Input: HL = year. ;; Output: Carry flag set if HL is a leap year. ;; Registers used: all. leap: mvi a,3 ; Divisible by 4? ana l ; If not, not a leap year, rnz ; Return w/carry cleared mvi b,2 ; Divide by 4 (shift right 2) leapdiv4: mov a,h rar mov h,a mov a,l rar mov l,a dcr b jnz leapdiv4 lxi b,-1 ; Divide by 25 using subtraction lxi d,-25 leapdiv25: inx b ; Keep quotient in BC dad d jc leapdiv25 mov a,e ; If so, L==E afterwards. xra l ; (High byte is always FF.) stc ; Set carry, and rnz ; return if not divisible. mvi a,3 ; Is this divisble by 4? ana c sui 1 ; Set carry if so. ret ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; Test code: get year from CP/M command line and see ;; if it is a leap year. test: lxi b,5Dh ; First char of "file name" lxi h,0 ; Accumulator digit: ldax b ; Get character sui '0' ; ASCII digit jc getleap ; Not valid digit = done cpi 10 jnc getleap ; Not valid digit = done dad h ; HL *= 10 mov d,h mov e,l dad h dad h dad d mvi d,0 ; Plus digit mov e,a dad d inx b ; Next character jmp digit getleap: call leap ; Is HL a leap year? lxi d,no ; No, jnc out ; unless carry is set, lxi d,yes ; then it is a leap year. out: mvi c,9 jmp 5 no: db 'NOT ' yes: db 'LEAP YEAR.\$'</lang>

## ActionScript

<lang actionscript>public function isLeapYear(year:int):Boolean {

```   if (year % 100 == 0) {
return (year % 400 == 0);
}
return (year % 4 == 0);
```

}</lang>

<lang Ada>-- Incomplete code, just a sniplet to do the task. Can be used in any package or method. -- Adjust the type of Year if you use a different one. function Is_Leap_Year (Year : Integer) return Boolean is begin

```  if Year rem 100 = 0 then
return Year rem 400 = 0;
else
return Year rem 4 = 0;
end if;
```

end Is_Leap_Year;

-- An enhanced, more efficient version: -- This version only does the 2 bit comparison (rem 4) if false. -- It then checks rem 16 (a 4 bit comparison), and only if those are not -- conclusive, calls rem 100, which is the most expensive operation. -- I failed to be convinced of the accuracy of the algorithm at first, -- so I rephrased it below. -- FYI: 400 is evenly divisible by 16 whereas 100,200 and 300 are not. Ergo, the -- set of integers evenly divisible by 16 and 100 are all evenly divisible by 400. -- 1. If a year is not divisible by 4 => not a leap year. Skip other checks. -- 2. If a year is evenly divisible by 16, it is either evenly divisible by 400 or -- not evenly divisible by 100 => leap year. Skip further checks. -- 3. If a year evenly divisible by 100 => not a leap year. -- 4. Otherwise a leap year.

function Is_Leap_Year (Year : Integer) return Boolean is begin

```  return (Year rem 4 = 0) and then ((Year rem 16 = 0) or else (Year rem 100 /= 0));
```

end Is_Leap_Year;

-- To improve speed a bit more, use with pragma Inline (Is_Leap_Year);</lang>

## ALGOL 60

Works with: A60

<lang algol60>begin integer year;

integer procedure mod(i,j); value i,j; integer i,j; mod:=i-(i div j)*j;

boolean procedure isLeapYear(year); value year; integer year; isLeapYear:=mod(year,400)=0 or (mod(year,4)=0 and mod(year,100) notequal 0);

for year := 1899, 1900, 1901, 1902, 1903, 1904, 1905, 1999, 2000, 2001, 2002, 2003, 2004 do begin outinteger(1,year); if isLeapYear(year) then outstring(1,"True\n") else outstring(1, "False\n") end for year end </lang>

Output:
``` 1899 False
1900 False
1901 False
1902 False
1903 False
1904 True
1905 False
1999 False
2000 True
2001 False
2002 False
2003 False
2004 True
```

## ALGOL 68

Works with: ALGOL 68 version Revision 1 - no extensions to language used
Works with: ALGOL 68G version Any - tested with release 1.18.0-9h.tiny

<lang algol68>MODE YEAR = INT, MONTH = INT, DAY = INT;

PROC year days = (YEAR year)DAY: # Ignore 1752 CE for the moment #

``` ( month days(year, 2) = 28 | 365 | 366 );

```

PROC month days = (YEAR year, MONTH month) DAY:

``` ( month | 31,
28 + ABS (year MOD 4 = 0 AND year MOD 100 /= 0 OR year MOD 400 = 0),
31, 30, 31, 30, 31, 31, 30, 31, 30, 31);

```

PROC is leap year = (YEAR year)BOOL: year days(year)=366;

test:(

``` []INT test cases = (1900, 1994, 1996, 1997, 2000);
FOR i TO UPB test cases DO
YEAR year = test cases[i];
printf((\$g(0)" is "b("","not ")"a leap year."l\$, year, is leap year(year)))
OD
```

)</lang>

Output:
```1900 is not a leap year.
1994 is not a leap year.
1996 is a leap year.
1997 is not a leap year.
2000 is a leap year.
```

## ALGOL W

<lang algolw>begin

```   % returns true if year is a leap year, false otherwise %
% assumes year is in the Gregorian Calendar            %
logical procedure isLeapYear ( integer value year ) ;
year rem 400 = 0 or ( year rem 4 = 0 and year rem 100 not = 0 );
```
```   % some test cases                                      %
for year := 1899, 1900, 1901, 1902, 1903, 1904, 1905, 1999, 2000, 2001, 2002, 2003, 2004 do begin
write( i_w := 1, s_w := 0
, year
, " is "
, if isLeapYear( year ) then "" else "not "
, " a leap year"
)
end for_year
```

end.</lang>

## ALGOL-M

<lang algol> BEGIN

% COMPUTE P MOD Q % INTEGER FUNCTION MOD(P, Q); INTEGER P, Q; BEGIN

``` MOD := P - Q * (P / Q);
```

END;

% RETURN 1 IF Y IS A LEAP YEAR, OTHERWISE 0 % INTEGER FUNCTION ISLEAP(Y); INTEGER Y; BEGIN

``` IF MOD(Y,4) <> 0 THEN    % QUICK EXIT IN MOST CASES %
ISLEAP := 0
ELSE IF MOD(Y,400) = 0 THEN
ISLEAP := 1
ELSE IF MOD(Y,100) = 0 THEN
ISLEAP := 0
ELSE                     % NON-CENTURY DIVISIBLE BY 4 %
ISLEAP := 1;
```

END;

% EXERCISE THE FUNCTION % INTEGER Y; WRITE("TEST OF CENTURY YEARS"); FOR Y := 1600 STEP 100 UNTIL 2000 DO

``` BEGIN
IF ISLEAP(Y) <> 0 THEN
WRITE(Y, " IS A LEAP YEAR")
ELSE
WRITE(Y, " IS NOT A LEAP YEAR");
END;
```

WRITE("TEST OF CURRENT DECADE"); FOR Y := 2010 STEP 1 UNTIL 2020 DO

``` BEGIN
IF ISLEAP(Y) <> 0 THEN
WRITE(Y, " IS A LEAP YEAR")
ELSE
WRITE(Y, " IS NOT A LEAP YEAR");
END;
```

END </lang>

Output:
```TEST OF CENTURY YEARS
1600 IS A LEAP YEAR
1700 IS NOT A LEAP YEAR
1800 IS NOT A LEAP YEAR
1900 IS NOT A LEAP YEAR
2000 IS A LEAP YEAR
2010 IS NOT A LEAP YEAR
2011 IS NOT A LEAP YEAR
2012 IS A LEAP YEAR
2013 IS NOT A LEAP YEAR
2014 IS NOT A LEAP YEAR
2015 IS NOT A LEAP YEAR
2016 IS A LEAP YEAR
2017 IS NOT A LEAP YEAR
2018 IS NOT A LEAP YEAR
2019 IS NOT A LEAP YEAR
2020 IS A LEAP YEAR
```

## APL

Returns 1 if leap year, 0 otherwise: <lang apl> ∇ z←Leap year Z←(0=4|year)∧(0=400|year)∨~0=100|year ∇ </lang> A much neater version of the above relies on the fact that every rule is an exception the the previous one: <lang apl> ∇ z←Leap year

``` z←0≠.=400 100 4∘.|year
```

∇ </lang> This essentially works by running an XOR reduction over the divisibility by 4, 100, and 400. Some APL implementations support tacit (a.k.a. points-free) programming: <lang apl> Leap←0≠.=400 100 4∘.|⊢ </lang> Dyalog APL version 18.0 added a built-in date-time function: <lang apl> Leap←0⎕DT,∘2 29¨ </lang> This works by extending the year to February 29 of that year, and then checking if the date is valid.

With any of the above definitions, no loop is necessary to check each year of an array: <lang apl>

```     Leap 1899 1900 1901 1902 1903 1904 1905 1999 2000 2001 2002 2003 2004
```

</lang>

Output:

<lang apl> 0 0 0 0 0 1 0 0 1 0 0 0 1 </lang>

## AppleScript

<lang applescript>on leap_year(y)

```   return y mod 4 is equal to 0 and (y mod 100 is not equal to 0 or y mod 400 is equal to 0)
```

end leap_year

leap_year(1900)</lang>

## Arc

<lang arc> (= leap? (fn (year)

``` (if (and (is 0 (mod year 4)) (isnt 0 (mod year 100))) year
(unless (< 0 (+ (mod year 100) (mod year 400))) year))))
```

</lang> Output: <lang arc> (map [leap? _] '(1900 1904 2000 2019 2020 2100))

=> '( 1904 2000 2020 )

</lang>

## Arturo

<lang rebol>years: [

```   1600 1660 1724 1788 1848 1912 1972
2032 2092 2156 2220 2280 2344 2348
1698 1699 1700 1750 1800 1810 1900
1901 1973 2100 2107 2200 2203 2289
```

]

print select years => leap?</lang>

Output:
`1600 1660 1724 1788 1848 1912 1972 2032 2092 2156 2220 2280 2344 2348`

## AutoHotkey

<lang autohotkey>leapyear(year) {

```   if (Mod(year, 100) = 0)
return (Mod(year, 400) = 0)
return (Mod(year, 4) = 0)
```

}

MsgBox, % leapyear(1604)</lang>

Output:
`Returns 1 if year is a leap year`

or <lang autohotkey>IsLeapYear(Year) {

```   return !Mod(Year, 4) && Mod(Year, 100) || !Mod(Year, 400)
```

}

MsgBox % "The year 1604 was " (IsLeapYear(1604) ? "" : "not ") "a leap year"</lang>

Output:
```The year 1600 was a leap year
The year 1601 was not a leap year
The year 1604 was a leap year```

## AutoIt

<lang AutoIt>; AutoIt Version: 3.3.8.1 \$Year = 2012 \$sNot = " not"

If IsLeapYear(\$Year) Then \$sNot = "" ConsoleWrite (\$Year & " is" & \$sNot & " a leap year." & @LF)

Func IsLeapYear(\$_year) Return Not Mod(\$_year, 4) And (Mod(\$_year, 100) Or Not Mod(\$_year, 400)) EndFunc

== But it exists the standard UDF "Date.au3" with this function
"_IsLeapYear(\$Year)"

</lang>

Output:
```2012 is a leap year.
```

--BugFix (talk) 16:18, 16 November 2013 (UTC)

## AWK

<lang AWK>function leapyear( year ) {

```   if ( year % 100 == 0 )
return ( year % 400 == 0 )
else
return ( year % 4 == 0 )
```

}</lang>

## Bash

<lang Bash>

1. !/bin/bash

is_leap_year () # Define function named is_leap_year {

declare -i year=\$1 # declare integer variable "year" and set it to function parm 1

echo -n "\$year (\$2)-> " # print the year passed in, but do not go to the next line

if (( \$year % 4 == 0 )) # if year not dividable by 4, then not a leap year, % is the modulus operator then

```       if (( \$year % 400 == 0 ))       # if century dividable by 400, is a leap year
then
echo "This is a leap year"
else
if (( \$year % 100 == 0 )) # if century not divisible by 400, not a leap year
then
echo "This is not a leap year"
else
echo "This is a leap year" # not a century boundary, but dividable by 4, is a leap year
fi
fi
```

else

```       echo "This is not a leap year"
```

fi

}

1. test all cases
2. call the function is_leap_year several times with two parameters... year and test's expectation for 'is/not leap year.

is_leap_year 1900 not # a leap year is_leap_year 2000 is # a leap year is_leap_year 2001 not # a leap year is_leap_year 2003 not # a leap year is_leap_year 2004 is # a leap year

1. Save the above to a file named is_leap_year.sh, then issue the following command to run the 5 tests of the function
2. bash is_leap_year.sh

</lang>

## BASIC

Works with: QBasic

Note that the `year%` function is not needed for most modern BASICs. <lang qbasic>DECLARE FUNCTION diy% (y AS INTEGER) DECLARE FUNCTION isLeapYear% (yr AS INTEGER) DECLARE FUNCTION year% (date AS STRING)

PRINT isLeapYear(year(DATE\$))

FUNCTION diy% (y AS INTEGER)

```   IF y MOD 4 THEN
diy = 365
ELSEIF y MOD 100 THEN
diy = 366
ELSEIF y MOD 400 THEN
diy = 365
ELSE
diy = 366
END IF
```

END FUNCTION

FUNCTION isLeapYear% (yr AS INTEGER)

```   isLeapYear = (366 = diy(yr))
```

END FUNCTION

FUNCTION year% (date AS STRING)

```   year% = VAL(RIGHT\$(date, 4))
```

END FUNCTION</lang>

An old-timey solution:

Works with: Commodore BASIC

<lang BASIC>10 DEF FNLY(Y)=(Y/4=INT(Y/4))*((Y/100<>INT(Y/100))+(Y/400=INT(Y/400)))</lang>

### GW-BASIC

Prints all the leap years from 1750 to 2021. Note the correct behaviour of 1800, 1900, and 2000. <lang gwbasic>10 FOR Y = 1750 TO 2021 20 GOSUB 1000 30 IF L = 1 THEN PRINT Y;" "; 40 NEXT Y 50 END 1000 L = 0 1010 IF Y MOD 4 <> 0 THEN RETURN 1020 IF Y MOD 100 = 0 AND Y MOD 400 <> 0 THEN RETURN 1030 L = 1 1040 RETURN</lang>

Output:
```
1752   1756   1760   1764   1768   1772   1776   1780   1784   1788   1792   1796   1804   1808   1812   1816   1820   1824   1828
1832   1836   1840   1844   1848   1852   1856   1860   1864   1868   1872   1876   1880   1884   1888   1892   1896   1904   1908   1912   1916   1920   1924   1928   1932   1936   1940   1944   1948   1952   1956   1960   1964   1968   1972   1976   1980

1984   1988   1992   1996   2000   2004   2008   2012   2016   2020```

### IS-BASIC

<lang IS-BASIC>100 PROGRAM "Leapyear.bas" 110 FOR I=1990 TO 2020 120 IF LEAPY(I) THEN 130 PRINT I;"is a leap year." 140 ELSE 150 PRINT I;"is not a leap year." 160 END IF 170 NEXT 180 DEF LEAPY(Y)=MOD(Y,4)=0 AND MOD(Y,100) OR MOD(Y,400)=0</lang>

### Sinclair ZX81 BASIC

ZX81 BASIC does not support user-defined functions, even the single-expression functions that are provided by many contemporary dialects; so we have to fake it using a subroutine and pass everything in global variables. <lang basic>5000 LET L=Y/4=INT (Y/4) AND (Y/100<>INT (Y/100) OR Y/400=INT (Y/400)) 5010 RETURN</lang> An example showing how to call it: <lang basic>10 INPUT Y 20 GOSUB 5000 30 PRINT Y;" IS "; 40 IF NOT L THEN PRINT "NOT "; 50 PRINT "A LEAP YEAR." 60 STOP</lang>

### ZX Spectrum Basic

<lang zxbasic>10 DEF FN l(y)=y/4=INT (y/4) AND (y/100<>INT (y/100) OR y/400=INT (y/400)) </lang>

### QL SuperBASIC

<lang qbasic> AUTO

```  REM Is% a non-proleptic Gregorian year y\$<=9999 leap (0) 0R ordinary (1)?
DEF FN Is%(y\$)
LOC l%,c%,y%
LET c%=y\$(1 TO 2)&"00" : y%=y\$
LET l%=c% MOD 16 AND y\$(3 TO 4)="00" OR y% MOD 4
RET l%
END DEF Is%
```

ctrl+space </lang> using only power-of-2 divisions. N.B. the inverted logic brings home the BaCon code's flaw

Output:
```1600  0
1700  1
1800  1
1900  1
2000  0
2100  1
```

### BaCon

From the Ada shortcut calculation <lang qbasic>' Leap year FUNCTION leapyear(NUMBER y) TYPE NUMBER

```  RETURN IIF(MOD(y, 4) = 0, IIF(MOD(y, 16) = 0, IIF(MOD(y, 100) != 0, TRUE, FALSE), TRUE), FALSE)
```

END FUNCTION

READ y WHILE y != 0

```   PRINT y, ": ", IIF\$(leapyear(y), "", "not a "), "leapyear"
```

WEND

DATA 1600, 1700, 1800, 1900, 1901, 1996, 2000, 2001, 2004, 0</lang>

Output:
```1600: not a leapyear
1700: leapyear
1800: leapyear
1900: leapyear
1901: not a leapyear
1996: leapyear
2000: not a leapyear
2001: not a leapyear
2004: leapyear
```

## Batch File

<lang dos>@echo off

The Main Thing...

for %%x in (1900 2046 2012 1600 1800 2031 1952) do ( call :leap %%x ) echo. pause exit/b

/The Main Thing...
The Function...
leap

set year=%1 set /a op1=%year%%%4 set /a op2=%year%%%100 set /a op3=%year%%%400 if not "%op1%"=="0" (goto :no) if not "%op2%"=="0" (goto :yes) if not "%op3%"=="0" (goto :no)

yes

echo. echo %year% is a leap year. goto :EOF

no

echo. echo %year% is NOT a leap year. goto :EOF

/The Function...</lang>
Output:
```1900 is NOT a leap year.

2046 is NOT a leap year.

2012 is a leap year.

1600 is a leap year.

1800 is NOT a leap year.

2031 is NOT a leap year.

1952 is a leap year.

Press any key to continue . . .```

## BBC BASIC

<lang bbcbasic> REPEAT

```       INPUT "Enter a year: " year%
IF FNleap(year%) THEN
PRINT ;year% " is a leap year"
ELSE
PRINT ;year% " is not a leap year"
ENDIF
UNTIL FALSE
END

DEF FNleap(yr%)
= (yr% MOD 4 = 0) AND ((yr% MOD 400 = 0) OR (yr% MOD 100 <> 0))</lang>
```

## Befunge

Translation of: C

<lang befunge>0"2("*:3-:1-:2-:"^"-v< v*%"d"\!%4::,,"is".:<| >\45*:*%!+#v_ "ton"vv< v"ear."+550<,,,,*84<\$# >"y pael a ">:#,_\$:#@^</lang>

Output:
```1900 is not a leap year.
1994 is not a leap year.
1996 is a leap year.
1997 is not a leap year.
2000 is a leap year.```

## Bracmat

<lang bracmat> ( leap-year

``` =
.     mod\$(!arg.100):0
& `(mod\$(!arg.400):0) { The backtick skips the remainder of the OR operation,
even if the tested condition fails. }
| mod\$(!arg.4):0
)
```

& 1600 1700 1899 1900 2000 2006 2012:?tests & whl

``` ' ( !tests:%?test ?tests
& ( leap-year\$!test&out\$(!test " is a leap year")
| out\$(!test " is not a leap year")
)
)
```

& ;</lang>

Output:
```1600  is a leap year
1700  is not a leap year
1899  is not a leap year
1900  is not a leap year
2000  is a leap year
2006  is not a leap year
2012  is a leap year```

## C

<lang c>#include <stdio.h>

int is_leap_year(int year) {

```   return (!(year % 4) && year % 100 || !(year % 400)) ? 1 : 0;
```

}

int main() {

```   int test_case[] = {1900, 1994, 1996, 1997, 2000}, key, end, year;
for (key = 0, end = sizeof(test_case)/sizeof(test_case[0]); key < end; ++key) {
year = test_case[key];
printf("%d is %sa leap year.\n", year, (is_leap_year(year) == 1 ? "" : "not "));
}
```

}</lang>

Output:
```1900 is not a leap year.
1994 is not a leap year.
1996 is a leap year.
1997 is not a leap year.
2000 is a leap year.
```

## C#

<lang csharp>using System;

class Program {

```   static void Main()
{
foreach (var year in new[] { 1900, 1994, 1996, DateTime.Now.Year })
{
Console.WriteLine("{0} is {1}a leap year.",
year,
DateTime.IsLeapYear(year) ? string.Empty : "not ");
}
}
```

}</lang>

Output:
```1900 is not a leap year.
1994 is not a leap year.
1996 is a leap year.
2010 is not a leap year.```

## C++

Uses C++11. Compile with

```g++ -std=c++11 leap_year.cpp
```

<lang cpp>#include <iostream>

bool is_leap_year(int year) {

``` return year % 4 == 0 && (year % 100 != 0 || year % 400 == 0);
```

}

int main() {

``` for (auto year : {1900, 1994, 1996, 1997, 2000}) {
std::cout << year << (is_leap_year(year) ? " is" : " is not") << " a leap year.\n";
}
```

}</lang>

Output:
```1900 is not a leap year.
1994 is not a leap year.
1996 is a leap year.
1997 is not a leap year.
2000 is a leap year.
```

## Clipper

<lang Clipper>Function IsLeapYear( nYear ) Return Iif( nYear%100 == 0, (nYear%400 == 0), (nYear%4 == 0) )</lang>

## Clojure

<lang clojure>(defn leap-year? [y]

``` (and (zero? (mod y 4)) (or (pos? (mod y 100)) (zero? (mod y 400)))))</lang>
```

## COBOL

<lang cobol> IDENTIFICATION DIVISION.

```      PROGRAM-ID. leap-year.
```
```      DATA DIVISION.
WORKING-STORAGE SECTION.
01  examples VALUE "19001994199619972000".
03  year PIC 9(4) OCCURS 5 TIMES
INDEXED BY year-index.
```
```      01  remainders.
03 400-rem   PIC 9(4).
03 100-rem   PIC 9(4).
03 4-rem     PIC 9(4).
```
```      PROCEDURE DIVISION.
PERFORM VARYING year-index FROM 1 BY 1 UNTIL 5 < year-index
MOVE FUNCTION MOD(year (year-index), 400) TO 400-rem
MOVE FUNCTION MOD(year (year-index), 100) TO 100-rem
MOVE FUNCTION MOD(year (year-index), 4) TO 4-rem
```
```              IF 400-rem = 0 OR ((100-rem NOT = 0) AND 4-rem = 0)
DISPLAY year (year-index) " is a leap year."
ELSE
DISPLAY year (year-index) " is not a leap year."
END-IF
END-PERFORM
```
```          GOBACK
.</lang>
```

Using Date Intrinsic Functions <lang COBOL>

```      program-id. leap-yr.
*> Given a year, where 1601 <= year <= 9999
*> Determine if the year is a leap year
data division.
working-storage section.
1 input-year pic 9999.
1 binary.
2 int-date pic 9(8).
2 cal-mo-day pic 9(4).
procedure division.
display "Enter calendar year (1601 thru 9999): "
accept input-year
if input-year >= 1601 and <= 9999
then
*> if the 60th day of a year is Feb 29
*> then the year is a leap year
compute int-date = function integer-of-day
( input-year * 1000 + 60 )
compute cal-mo-day = function mod (
(function date-of-integer ( int-date )) 10000 )
display "Year " input-year space with no advancing
if cal-mo-day = 229
display "is a leap year"
else
display "is NOT a leap year"
end-if
else
display "Input date is not within range"
end-if
stop run
.
end program leap-yr.
```

</lang>

Output:
```Enter calendar year (1601 thru 9999): 2016
Year 2016 is a leap year
Enter calendar year (1601 thru 9999): 2017
Year 2017 is NOT a leap year
Enter calendar year (1601 thru 9999): 2100
Year 2100 is NOT a leap year
Enter calendar year (1601 thru 9999): 2400
Year 2400 is a leap year
Enter calendar year (1601 thru 9999): 3000
Year 3000 is NOT a leap year
Enter calendar year (1601 thru 9999): 4000
Year 4000 is a leap year
```

## Common Lisp

<lang lisp>(defun leap-year-p (year)

``` (destructuring-bind (fh h f)
(mapcar #'(lambda (n) (zerop (mod year n))) '(400 100 4))
(or fh (and (not h) f))))</lang>
```

## Component Pascal

BlackBox Component Builder <lang oberon2> MODULE LeapYear; IMPORT StdLog, Strings, Args;

PROCEDURE IsLeapYear(year: INTEGER): BOOLEAN; BEGIN IF year MOD 4 # 0 THEN

```   	RETURN FALSE
```

ELSE IF year MOD 100 = 0 THEN IF year MOD 400 = 0 THEN RETURN TRUE ELSE RETURN FALSE END ELSE RETURN TRUE END END END IsLeapYear;

PROCEDURE Do*; VAR p: Args.Params; year,done,i: INTEGER; BEGIN Args.Get(p); FOR i := 0 TO p.argc - 1 DO Strings.StringToInt(p.args[i],year,done); StdLog.Int(year);StdLog.String(":>");StdLog.Bool(IsLeapYear(year));StdLog.Ln END;

END Do; END LeapYear. </lang> Execute: ^Q LeapYear.Do 2000 2004 2013~

Output:
``` 2000:> \$TRUE
2004:> \$TRUE
2013:> \$FALSE
```

## Crystal

<lang ruby>p Time.leap_year?(2020) p Time.leap_year?(2021) p Time.leap_year?(2022)</lang>

```true
false
false
```

## D

<lang d>import std.algorithm;

bool leapYear(in uint y) pure nothrow {

```   return (y % 4) == 0 && (y % 100 || (y % 400) == 0);
```

}

void main() {

```   auto good = [1600, 1660, 1724, 1788, 1848, 1912, 1972, 2032,
2092, 2156, 2220, 2280, 2344, 2348];
auto bad =  [1698, 1699, 1700, 1750, 1800, 1810, 1900, 1901,
1973, 2100, 2107, 2200, 2203, 2289];
```

}</lang>

Using the datetime library: <lang d>import std.datetime;

void main() {

```   assert(yearIsLeapYear(1724));
assert(!yearIsLeapYear(1973));
assert(!Date(1900, 1, 1).isLeapYear);
assert(DateTime(2000, 1, 1).isLeapYear);
```

} </lang>

## Dart

<lang Dart>class Leap {

``` bool leapYear(num year) {
return (year % 400 == 0) || (( year % 100 != 0) && (year % 4 == 0));
```
``` bool isLeapYear(int year) =>
(year % 4 == 0) && ((year % 100 != 0) || (year % 400 == 0));
// Source: https://api.flutter.dev/flutter/quiver.time/isLeapYear.html
}
```

}</lang>

## Dc

Directly taken from Wikipedia.

Works with: GNU dc

<lang Dc>[0q]s0 [1q]s1

[ S. [ l. 4% 0!=0 ## if y % 4: return 0

```       l. 100% 0!=1    ## if y % 100:  return 1
l. 400% 0!=0    ## if y % 400:  return 0
1               ##              return 1
]x s.L.
```

]sL ## L = isleapYear()

[ Sy

```   lyn [ is ]P
ly lLx
[not ] 0:y
[    ] 1:y
;yP
[a leap year]P AP
OsyLyo
```

]sT ## T = testYear()

1988 lTx 1989 lTx 1900 lTx 2000 lTx</lang>

Output:
```1988 is     a leap year
1989 is not a leap year
1900 is not a leap year
2000 is     a leap year
```

## Delphi/Pascal

Delphi has standard function IsLeapYear in SysUtils unit. <lang Delphi>program TestLeapYear;

{\$APPTYPE CONSOLE}

uses

``` SysUtils;
```

var

``` Year: Integer;
```

begin

``` Write('Enter the year: ');
if IsLeapYear(Year) then
Writeln(Year, ' is a Leap year')
else
Writeln(Year, ' is not a Leap year');
```

end.</lang>

## DWScript

<lang Delphi>function IsLeapYear(y : Integer) : Boolean; begin

```  Result:=    (y mod 4 = 0)
and (   ((y mod 100) <> 0)
or ((y mod 400) = 0) );
```

end;

const good : array [0..13] of Integer =

```  [1600,1660,1724,1788,1848,1912,1972,2032,2092,2156,2220,2280,2344,2348];
```

const bad : array [0..13] of Integer =

```  [1698,1699,1700,1750,1800,1810,1900,1901,1973,2100,2107,2200,2203,2289];
```

var i : Integer;

PrintLn('Checking leap years'); for i in good do

```  if not IsLeapYear(i) then PrintLn(i);
```

PrintLn('Checking non-leap years'); for i in bad do

```  if IsLeapYear(i) then PrintLn(i);</lang>
```

## Dyalect

<lang Dyalect>func isLeap(y) {

```   if y % 100 == 0 {
y % 400 == 0
} else {
y % 4 == 0
}
```

}

print(isLeap(1984))</lang>

Output:
`true`

## Ela

<lang ela>isLeap y | y % 100 == 0 = y % 400 == 0

```        | else         = y % 4 == 0</lang>
```

## Elixir

<lang elixir>leap_year? = fn(year) -> :calendar.is_leap_year(year) end IO.inspect for y <- 2000..2020, leap_year?.(y), do: y</lang>

Output:
```[2000, 2004, 2008, 2012, 2016, 2020]
```

## Emacs Lisp

Translation of: Scheme

<lang lisp>(defun leap-year-p (year)

``` (apply (lambda (a b c) (or a (and (not b) c)))
```

(mapcar (lambda (n) (zerop (mod year n))) '(400 100 4))))</lang>

## Erlang

<lang erlang> -module(gregorian). -export([leap/1]).

leap( Year ) -> calendar:is_leap_year( Year ). </lang>

## ERRE

<lang ERRE>PROGRAM LEAP_YEAR

FUNCTION LEAP(YR%)

```    LEAP=(YR% MOD 4=0) AND ((YR% MOD 400=0) OR (YR% MOD 100<>0))
```

END FUNCTION

BEGIN

```    LOOP
INPUT("Enter a year: ",year%)
EXIT IF YEAR%=0
IF LEAP(year%) THEN
PRINT(year%;" is a leap year")
ELSE
PRINT(year%;" is not a leap year")
END IF
END LOOP
```

END PROGRAM</lang>

## Euphoria

<lang euphoria>function isLeapYear(integer year)

```   return remainder(year,4)=0 and remainder(year,100)!=0 or remainder(year,400)=0
```

end function</lang>

## Excel

Take two cells, say A1 and B1, in B1 type in :

<lang Excel> =IF(OR(NOT(MOD(A1,400)),AND(NOT(MOD(A1,4)),MOD(A1,100))),"Leap Year","Not a Leap Year") </lang>

Output:
```1900	Not a Leap Year
1954	Not a Leap Year
1996	Leap Year
2003	Not a Leap Year
2012	Leap Year
```

## F#

<lang fsharp>let isLeapYear = System.DateTime.IsLeapYear assert isLeapYear 1996 assert isLeapYear 2000 assert not (isLeapYear 2001) assert not (isLeapYear 1900)</lang>

## Factor

Call leap-year? word from calendars vocabulary. For example: <lang factor>USING: calendar prettyprint ; 2011 leap-year? .</lang> Factor uses proleptic Gregorian calendar.

## Fermat

<lang>Function IsLeap(y) = if y|4>0 then 0 else if y|100=0 and y|400>0 then 0 else 1 fi fi.</lang>

## Forth

<lang forth>: leap-year? ( y -- ? )

``` dup 400 mod 0= if drop true  exit then
dup 100 mod 0= if drop false exit then
4 mod 0= ;</lang>
```

Or more simply (but always computing three "mod"): <lang forth>: leap-year? dup 4 mod 0= over 16 mod 0= rot 25 mod 0= not or and ;</lang>

## Fortran

<lang fortran>program leap

```implicit none
```
```write(*,*) leap_year([1900, 1996, 1997, 2000])
```
```contains
```

pure elemental function leap_year(y) result(is_leap) implicit none logical :: is_leap integer,intent(in) :: y

is_leap = (mod(y,4)==0 .and. .not. mod(y,100)==0) .or. (mod(y,400)==0)

end function leap_year

end program leap</lang>

Output:
`  F T F T `

## FreeBASIC

<lang FreeBASIC>' version 23-06-2015 ' compile with: fbc -s console

1. Ifndef TRUE ' define true and false for older freebasic versions
```   #Define FALSE 0
#Define TRUE Not FALSE
```
1. EndIf

Function leapyear(Year_ As Integer) As Integer

```   If (Year_ Mod 4) <> 0 Then Return FALSE
If (Year_ Mod 100) = 0 AndAlso (Year_ Mod 400) <> 0 Then Return FALSE
Return TRUE
```

End Function

' ------=< MAIN >=------

' year is a FreeBASIC keyword Dim As Integer Year_

For Year_ = 1800 To 2900 Step 100

```   Print Year_; IIf(leapyear(Year_), " is a leap year", " is not a leap year")
```

Next

Print : Print

For Year_ = 2012 To 2031

```   Print Year_;
If leapyear(Year_) = TRUE Then
Print " = leap",
Else
Print " = no",
End If
If year_ Mod 4 = 3 Then Print ' lf/cr
```

Next

' empty keyboard buffer While InKey <> "" : Wend Print : Print "hit any key to end program" Sleep End</lang>

Output:
``` 1800 is not a leap year
1900 is not a leap year
2000 is a leap year
2100 is not a leap year
2200 is not a leap year
2300 is not a leap year
2400 is a leap year
2500 is not a leap year
2600 is not a leap year
2700 is not a leap year
2800 is a leap year
2900 is not a leap year

2012 = leap   2013 = no     2014 = no     2015 = no
2016 = leap   2017 = no     2018 = no     2019 = no
2020 = leap   2021 = no     2022 = no     2023 = no
2024 = leap   2025 = no     2026 = no     2027 = no
2028 = leap   2029 = no     2030 = no     2031 = no```

## FutureBasic

<lang futurebasic> include "ConsoleWindow"

// In-line C function to generate random number in range BeginCFunction long randomInRange( long min, long max ) { int i = (arc4random()%(max-min+1))+min; return (long)i; } EndC toolbox fn randomInRange( long min, long max ) = long

// Leap year test function local fn LeapYear( year as long ) as Boolean dim as Boolean result : result = _false

if year mod 400 == 0 then result = _true  : exit fn if year mod 100 == 0 then result = _false : exit fn if year mod 4 == 0 then result = _true  : exit fn if year mod 4 != 0 then result = _false : exit fn end fn = result

dim as long i, y, knownLeapYear(10)

// Array of known leap years from 1980 through 2020 for control knownLeapYear(0) = 1980 : knownLeapYear(1) = 1984 : knownLeapYear(2) = 1988 knownLeapYear(3) = 1992 : knownLeapYear(4) = 1996 : knownLeapYear(5) = 2000 knownLeapYear(6) = 2004 : knownLeapYear(7) = 2008 : knownLeapYear(8) = 2012 knownLeapYear(9) = 2016 : knownLeapYear(10) = 2020

print "Known leap years:" for i = 0 to 9

```  if ( fn LeapYear( knownLeapYear(i) ) == _true )
print knownLeapYear(i); " is a leap year."
```

else

```  print knownLeapYear(i); " is a not leap year."
end if
```

next

print

// Random years from 1980 to 2020 to test print "Check random years:" for i = 0 to 20

```  y = fn randomInRange( 1980, 2020  )
if ( fn LeapYear( y ) == _true )
print y; " is a leap year."
else
print y; " is a not leap year."
end if
```

next </lang>

Output (results will vary for random years):

```Known leap years:
1980 is a leap year.
1984 is a leap year.
1988 is a leap year.
1992 is a leap year.
1996 is a leap year.
2000 is a leap year.
2004 is a leap year.
2008 is a leap year.
2012 is a leap year.
2016 is a leap year.

Check random years:
1998 is a not leap year.
1987 is a not leap year.
2015 is a not leap year.
1998 is a not leap year.
2020 is a leap year.
2020 is a leap year.
2009 is a not leap year.
2020 is a leap year.
2018 is a not leap year.
2013 is a not leap year.
2003 is a not leap year.
1994 is a not leap year.
1989 is a not leap year.
1999 is a not leap year.
1984 is a leap year.
1980 is a leap year.
1998 is a not leap year.
2008 is a leap year.
1983 is a not leap year.
2007 is a not leap year.
2004 is a leap year.
```

## Gambas

<lang gambas>Public Sub Form_Open() Dim dDate As Date Dim siYear As Short = InputBox("Enter a year", "Leap year test") Dim sMessage As String = " is a leap year."

Try dDate = Date(siYear, 02, 29) If Error Then sMessage = " is not a leap year."

Message(siYear & sMessage)

End</lang>

Output:

```2016 is a leap year.
```

## GAP

<lang gap>IsLeapYear := function(n)

``` return (n mod 4 = 0) and ((n mod 100 <> 0) or (n mod 400 = 0));
```

end;

1. alternative using built-in function

IsLeapYear := function(n)

``` return DaysInYear(n) = 366;
```

end;</lang>

## Genie

Dialect conversion from Vala entry.

<lang genie>[indent=4] /*

```  Leap year, in Genie
```
```  valac leapYear.gs
./leapYear
```
• /

init

```   years:array of DateYear = {1900, 1994, 1996, 1997, 2000, 2100}
```
```   for year in years
status:string = year.is_leap_year() ? "" : "not "
stdout.printf("%d is %sa leap year.\n", year, status)</lang>
```
Output:
```prompt\$ valac leapYear.gs
prompt\$ ./leapYear
1900 is not a leap year.
1994 is not a leap year.
1996 is a leap year.
1997 is not a leap year.
2000 is a leap year.
2100 is not a leap year.```

## Go

<lang go>func isLeap(year int) bool {

```   return year%400 == 0 || year%4 == 0 && year%100 != 0
```

}</lang>

## Groovy

Solution: <lang groovy>(1900..2012).findAll {new GregorianCalendar().isLeapYear(it)}.each {println it}</lang>

Output:
```1904
1908
1912
1916
1920
1924
1928
1932
1936
1940
1944
1948
1952
1956
1960
1964
1968
1972
1976
1980
1984
1988
1992
1996
2000
2004
2008
2012```

## GW-BASIC

Works with: PC-BASIC version any

<lang qbasic> 10 ' Leap year 20 DEF FN ISLEAPYEAR(Y%) = ((Y% MOD 4 = 0) AND (Y% MOD 100 <> 0)) OR (Y% MOD 400 = 0) 95 ' *** Test *** 100 FOR I% = 1 TO 5 110 READ YEAR% 120 PRINT YEAR%; "is "; 130 IF FN ISLEAPYEAR(YEAR%) = 0 THEN PRINT "not "; ELSE PRINT ""; 140 PRINT "a leap year." 150 NEXT I% 160 END 200 DATA 1900, 1994, 1996, 1997, 2000 </lang>

Output:
``` 1900 is not a leap year.
1994 is not a leap year.
1996 is a leap year.
1997 is not a leap year.
2000 is a leap year.
```

## Harbour

<lang visualfoxpro>FUNCTION IsLeapYear( nYear )

```  RETURN iif( nYear % 100 == 0, nYear % 400 == 0, nYear % 4 == 0 )</lang>
```

leaptext x b | b = show x ++ " is a leap year" | otherwise = show x ++ " is not a leap year"

isleapsf j | 0==j`mod`100 = 0 == j`mod`400 | otherwise = 0 == j`mod`4</lang> Algorithmic <lang haskell>isleap = foldl1 ((&&).not).flip map [400, 100, 4]. ((0==).).mod</lang> Example using isleap <lang haskell>*Main> mapM_ (putStrLn. (ap leaptext isleap)) [1900,1994,1996,1997,2000] 1900 is not a leap year 1994 is not a leap year 1996 is a leap year 1997 is not a leap year 2000 is a leap year</lang>

isLeapYear::Int->Bool isLeapYear y

``` | mod y 400 == 0 = True
| mod y 100 == 0 = False
| mod y 4 == 0 = True
| otherwise = False
```

tests = TestList[TestCase \$ assertEqual "4 is a leap year" True \$ isLeapYear 4

```               ,TestCase \$ assertEqual "1 is not a leap year" False \$ isLeapYear 1
,TestCase \$ assertEqual "64 is a leap year" True \$ isLeapYear 64
,TestCase \$ assertEqual "2000 is a leap year" True \$ isLeapYear 2000
,TestCase \$ assertEqual "1900 is not a leap year" False \$ isLeapYear 1900]</lang>
```

## Hy

<lang clojure>(defn leap? [y]

```   (and
(= (% y 4) 0)
(or
(!= (% y 100) 0)
(= (% y 400) 0))))</lang>
```

## Icon and Unicon

Gives leap year status for 2000,1900,2012 and any arguments you give <lang Icon>procedure main(arglist) every y := !([2000,1900,2012]|||arglist) do

``` write("The year ",y," is ", leapyear(y) | "not ","a leap year.")
```

end

procedure leapyear(year) #: determine if year is leap

```  if (numeric(year) % 4 = 0 & year % 100 ~= 0) | (numeric(year) % 400 = 0) then return
```

end</lang>

## J

<lang j>isLeap=: 0 -/@:= 4 100 400 |/ ]</lang> Example use: <lang j> isLeap 1900 1996 1997 2000 0 1 0 1</lang>

## Java

By default, java.util.GregorianCalendar switches from Julian calendar to Gregorian calendar at 15 October 1582. The code below uses both the GregorianCalendar class and the algorithm from the wiki. Both values are printed in the output.

<lang java>import java.util.GregorianCalendar; import java.text.MessageFormat;

public class Leapyear{

```       public static void main(String[] argv){
int[] yrs = {1800,1900,1994,1998,1999,2000,2001,2004,2100};
GregorianCalendar cal = new GregorianCalendar();
for(int year : yrs){
System.err.println(MessageFormat.format("The year {0,number,#} is leaper: {1} / {2}.",
year, cal.isLeapYear(year), isLeapYear(year)));
}
```
```       }
public static boolean isLeapYear(int year){
return (year % 100 == 0) ? (year % 400 == 0) : (year % 4 == 0);
}
```

}

</lang>

Output:
```The year 1800 is leaper: false / false.
The year 1900 is leaper: false / false.
The year 1994 is leaper: false / false.
The year 1998 is leaper: false / false.
The year 1999 is leaper: false / false.
The year 2000 is leaper: true / true.
The year 2001 is leaper: false / false.
The year 2004 is leaper: true / true.
The year 2100 is leaper: false / false.```
Works with: Java version 8

<lang java>import java.time.Year;

public class IsLeap {

```   public static void main(String[] args) {
System.out.println(Year.isLeap(2004));
}
```

} </lang>

## JavaScript

<lang javascript>var isLeapYear = function (year) { return (year % 100 === 0) ? (year % 400 === 0) : (year % 4 === 0); };</lang> Or, by setting the day to the 29th and checking if the day remains <lang javascript>// Month values start at 0, so 1 is for February var isLeapYear = function (year) { return new Date(year, 1, 29).getDate() === 29; };</lang>

## jq

Translation of: Julia

<lang jq>def leap:

``` . as \$y | (\$y%4) == 0 and (\$y < 1582 or (\$y%400) == 0 or (\$y%100) != 0);</lang>
```

Examples: <lang jq>def assert(value; f):

``` value as \$value
| (\$value|f) | if . then empty else error("assertion violation: \(\$value) => \(.)") end;
```

((2400, 2012, 2000, 1600, 1500, 1400) | assert(.; leap)),

((2100, 2014, 1900, 1800, 1700, 1499) | assert(.; leap|not)) </lang>

Output:
```\$ jq -n -f Leap_year.jq
```

## Julia

Works with: Julia version 0.6

<lang julia>isleap(yr::Integer) = yr % 4 == 0 && (yr < 1582 || yr % 400 == 0 || yr % 100 != 0)

@assert all(isleap, [2400, 2012, 2000, 1600, 1500, 1400]) @assert !any(isleap, [2100, 2014, 1900, 1800, 1700, 1499])</lang>

## K

<lang K> leapyear:{(+/~x!'4 100 400)!2}

```  a@&leapyear'a:1900,1994,1996,1997,2000
```

1996 2000</lang>

## Kotlin

<lang kotlin>fun isLeapYear(year: Int) = year % 400 == 0 || (year % 100 != 0 && year % 4 == 0)</lang>

## Lasso

<lang Lasso>define isLeapYear(y::integer) => { #y % 400 == 0 ? return true #y % 100 == 0 ? return false #y % 4 == 0 ? return true return false }

with test in array(2012,2016,1933,1900,1999,2000) do => {^ isLeapYear(#test) '\r' ^}</lang>

Output:
```true
true
false
false
false
true```

## Liberty BASIC

### Simple method

<lang lb>if leap(1996)then

```   print "leap"
```

else

```   print "ordinary"
```

end if wait

function leap(n)

```   leap=date\$("2/29/";n)
```

end function</lang>

### Calculated method

<lang lb> year = 1908

```   select case
case year mod 400 = 0
leapYear = 1
case year mod 4 = 0 and year mod 100 <> 0
leapYear = 1
case else
leapYear = 0
end select
if leapYear = 1 then
print year;" is a leap year."
else
print year;" is not a leap year."
end if</lang>
```

## Lingo

<lang lingo>on isLeapYear (year)

``` return date(year, 2, 29).month=2
```

end</lang>

## LiveCode

<lang LiveCode>function isLeapYear year

```   return (year MOD 4 is 0) AND ((year MOD 400 is 0) OR (year MOD 100 is not 0))
```

end isLeapYear

command testLeapYear

```   set itemDelimiter to comma
put  "1900,1994,1996,1997,2000" into years
repeat for each item y in years
put y && "is" && isLeapYear(y) && return after tyears
end repeat
put tyears
```

end testLeapYear

1900 is false 1994 is false 1996 is true 1997 is false 2000 is true </lang>

## LLVM

<lang llvm>; This is not strictly LLVM, as it uses the C library function "printf".

LLVM does not provide a way to print values, so the alternative would be
to just load the string into memory, and that would be boring.

\$"EMPTY_STR" = comdat any \$"NOT_STR" = comdat any \$"IS_A_LEAP_YEAR" = comdat any

@main.test_case = private unnamed_addr constant [5 x i32] [i32 1900, i32 1994, i32 1996, i32 1997, i32 2000], align 16 @"EMPTY_STR" = linkonce_odr unnamed_addr constant [1 x i8] zeroinitializer, comdat, align 1 @"NOT_STR" = linkonce_odr unnamed_addr constant [5 x i8] c"not \00", comdat, align 1 @"IS_A_LEAP_YEAR" = linkonce_odr unnamed_addr constant [22 x i8] c"%d is %sa leap year.\0A\00", comdat, align 1

--- The declaration for the external C printf function.

declare i32 @printf(i8*, ...)

Function Attrs
noinline nounwind optnone uwtable

define i32 @is_leap_year(i32) #0 {

``` %2 = alloca i32, align 4              ;-- allocate a local copy of year
store i32 %0, i32* %2, align 4        ;-- store a copy of year
```
``` %3 = load i32, i32* %2, align 4       ;-- load the year
%4 = srem i32 %3, 4                   ;-- year % 4
%5 = icmp ne i32 %4, 0                ;-- (year % 4) != 0
br i1 %5, label %c1false, label %c1true
```

c1true:

``` %6 = load i32, i32* %2, align 4       ;-- load the year
%7 = srem i32 %6, 100                 ;-- year % 100
%8 = icmp ne i32 %7, 0                ;-- (year % 100) != 0
br i1 %8, label %c2true, label %c1false
```

c1false:

``` %9 = load i32, i32* %2, align 4       ;-- load the year
%10 = srem i32 %9, 400                ;-- year % 400
%11 = icmp ne i32 %10, 0              ;-- (year % 400) != 0
%12 = xor i1 %11, true
br label %c2true
```

c2true:

``` %13 = phi i1 [ true, %c1true ], [ %12, %c1false ]
%14 = zext i1 %13 to i64
%15 = select i1 %13, i32 1, i32 0
ret i32 %15
```

}

Function Attrs
noinline nounwind optnone uwtable

define i32 @main() #0 {

``` %1 = alloca [5 x i32], align 16       ;-- allocate test_case
%2 = alloca i32, align 4              ;-- allocate key
%3 = alloca i32, align 4              ;-- allocate end
%4 = alloca i32, align 4              ;-- allocate year
%5 = bitcast [5 x i32]* %1 to i8*
call void @llvm.memcpy.p0i8.p0i8.i64(i8* %5, i8* bitcast ([5 x i32]* @main.test_case to i8*), i64 20, i32 16, i1 false)
store i32 0, i32* %2, align 4         ;-- store 0 in key
store i32 5, i32* %3, align 4         ;-- store 5 in end
br label %loop
```

loop:

``` %6 = load i32, i32* %2, align 4       ;-- load key
%8 = icmp slt i32 %6, %7              ;-- key < end
br i1 %8, label %loop_body, label %exit
```

loop_body:

``` %9 = load i32, i32* %2, align 4       ;-- load key
%10 = sext i32 %9 to i64              ;-- sign extend key
%11 = getelementptr inbounds [5 x i32], [5 x i32]* %1, i64 0, i64 %10
store i32 %12, i32* %4, align 4       ;-- store test_case[key] as year
```
``` %13 = load i32, i32* %4, align 4      ;-- load year
%14 = call i32 @is_leap_year(i32 %13) ;-- is_leap_year(year)
%15 = icmp eq i32 %14, 1              ;-- is_leap_year(year) == 1
%16 = zext i1 %15 to i64              ;-- zero extend
%17 = select i1 %15, i8* getelementptr inbounds ([1 x i8], [1 x i8]* @"EMPTY_STR", i32 0, i32 0), i8* getelementptr inbounds ([5 x i8], [5 x i8]* @"NOT_STR", i32 0, i32 0)
```
``` %18 = load i32, i32* %4, align 4      ;-- load year
%19 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([22 x i8], [22 x i8]* @"IS_A_LEAP_YEAR", i32 0, i32 0), i32 %18, i8* %17)
```
``` %20 = load i32, i32* %2, align 4      ;-- load key
%21 = add nsw i32 %20, 1              ;-- increment key
store i32 %21, i32* %2, align 4       ;-- store key
br label %loop
```

exit:

``` ret i32 0
```

}

Function Attrs
argmemonly nounwind

declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture writeonly, i8* nocapture readonly, i64, i32, i1) #1

attributes #0 = { noinline nounwind optnone uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" } attributes #1 = { argmemonly nounwind }</lang>

Output:
```1900 is not a leap year.
1994 is not a leap year.
1996 is a leap year.
1997 is not a leap year.
2000 is a leap year.```

## Logo

<lang logo>to multiple? :n :d

``` output equal? 0 modulo :n :d
```

end to leapyear? :y

``` output ifelse multiple? :y 100 [multiple? :y 400] [multiple? :y 4]
```

end</lang>

## Logtalk

<lang logtalk>leap_year(Year) :-

```   (   mod(Year, 4) =:= 0, mod(Year, 100) =\= 0 ->
true
;   mod(Year, 400) =:= 0
).</lang>
```

## LOLCODE

<lang lolcode>BTW Determine if a Gregorian calendar year is leap HAI 1.3 HOW IZ I Leap YR Year

``` BOTH SAEM 0 AN MOD OF Year AN 4
O RLY?
YA RLY
BOTH SAEM 0 AN MOD OF Year AN 100
O RLY?
YA RLY
BOTH SAEM 0 AN MOD OF Year AN 400
O RLY?
YA RLY
FOUND YR WIN
NO WAI
FOUND YR FAIL
OIC
NO WAI
FOUND YR WIN
OIC
NO WAI
FOUND YR FAIL
OIC
```

IF U SAY SO

I HAS A Yearz ITZ A BUKKIT Yearz HAS A SRS 0 ITZ 1900 Yearz HAS A SRS 1 ITZ 1904 Yearz HAS A SRS 2 ITZ 1994 Yearz HAS A SRS 3 ITZ 1996 Yearz HAS A SRS 4 ITZ 1997 Yearz HAS A SRS 5 ITZ 2000

IM IN YR Loop UPPIN YR Index WILE DIFFRINT Index AN 6

``` I HAS A Yr ITZ Yearz'Z SRS Index
I HAS A Not
I IZ Leap YR Yr MKAY
O RLY?
YA RLY
Not R ""
NO WAI
Not R " NOT"
OIC
VISIBLE Yr " is" Not " a leap year"
```

IM OUTTA YR Loop

KTHXBYE </lang>

Output:
```1900 is NOT a leap year
1904 is a leap year
1994 is NOT a leap year
1996 is a leap year
1997 is NOT a leap year
2000 is a leap year
```

## Lua

<lang Lua>function isLeapYear(year)

``` return year%4==0 and (year%100~=0 or year%400==0)
```

end</lang>

## Maple

<lang maple>isLeapYear := proc(year) if not year mod 4 = 0 or (year mod 100 = 0 and not year mod 400 = 0) then return false; else return true; end if; end proc:</lang>

## Mathematica

Dates are handled by built-in functions in the Wolfram Language <lang Mathematica>LeapYearQ[2002]</lang>

## MATLAB / Octave

MATLAB, conveniently, provides a function that returns the last day of an arbitrary month of the calendar given the year. Using the fact that February is 29 days long during a leap year, we can write a one-liner that solves this task. <lang MATLAB>function TrueFalse = isLeapYear(year)

```   TrueFalse = (eomday(year,2) == 29);
```

end</lang>

### Using Logical and modular functions

<lang matlab>x = ~mod(YEAR, 4) & (mod(YEAR, 100) | ~mod(YEAR, 400))</lang>

## Maxima

<lang maxima>leapyearp(year) := is(mod(year, 4) = 0 and

```  (mod(year, 100) # 0 or mod(year, 400) = 0))\$</lang>
```

## Mercury

<lang mercury>:- pred is_leap_year(int::in) is semidet.

is_leap_year(Year) :-

```  ( if Year mod 100 = 0 then Year mod 400 = 0 else Year mod 4 = 0 ).</lang>
```

Usage:

<lang mercury>:- module leap_year.

- interface.
- import_module io.
- pred main(io::di, io::uo) is det.
- implementation.
- import_module int, list, string.

main(!IO) :-

```   Years = [1600, 1700, 1899, 1900, 2000, 2006, 2012],
io.write_list(Years, "", write_year_kind, !IO).
```
- pred write_year_kind(int::in, io::di, io::uo) is det.

write_year_kind(Year, !IO) :-

``` io.format("%d %s a leap year.\n",
[i(Year), s(if is_leap_year(Year) then "is" else "is not" )], !IO).</lang>
```

## min

Works with: min version 0.19.6

<lang min>(mod 0 ==) :divisor? (((400 divisor?) (4 divisor?) (100 divisor? not)) cleave and or) :leap-year?</lang>

## MiniScript

<lang MiniScript>isLeapYear = function(year)

``` return year%4==0 and (year % 100 or not year % 400)
```

end function</lang>

## MIPS Assembly

Pass year in a0, returns boolean in v0. <lang mips> IsLeap: andi \$a1, \$a0, 3 #a0 is year to test bnez \$a1 NotLeap li \$a1, 100 div \$a0, \$a1 mfhi \$a1 bnez \$a1, Leap mflo \$a1 andi \$a1, \$a1, 3 bnez \$a1, NotLeap Leap: li \$v0, 1 jr \$ra NotLeap:li \$v0, 0 jr \$ra </lang>

## МК-61/52

<lang>П0 1 0 0 / {x} x=0 14 ИП0 4 0 0 ПП 18 ИП0 4 ПП 18 / {x} x=0 24 1 С/П 0 С/П</lang>

## Modula-2

<lang modula2>MODULE LeapYear; FROM FormatString IMPORT FormatString; FROM Terminal IMPORT WriteString,ReadChar;

PROCEDURE IsLeapYear(year : INTEGER) : BOOLEAN; BEGIN

```   IF year MOD 100 = 0 THEN
RETURN year MOD 400 = 0;
END;
RETURN year MOD 4 = 0
```

END IsLeapYear;

PROCEDURE Print(year : INTEGER); VAR

```   buf : ARRAY[0..63] OF CHAR;
leap : BOOLEAN;
```

BEGIN

```   leap := IsLeapYear(year);
FormatString("Is %i a leap year? %b\n", buf, year, leap);
WriteString(buf)
```

END Print;

BEGIN

```   Print(1900);
Print(1994);
Print(1996);
Print(1997);
Print(2000);
```

END LeapYear.</lang>

## MUMPS

<lang MUMPS>ILY(X) ;IS IT A LEAP YEAR?

```QUIT ((X#4=0)&(X#100'=0))!((X#100=0)&(X#400=0))</lang>
```

Usage:

```USER>W \$SELECT(\$\$ILY^ROSETTA(1900):"Yes",1:"No")
No
USER>W \$SELECT(\$\$ILY^ROSETTA(2000):"Yes",1:"No")
Yes
USER>W \$SELECT(\$\$ILY^ROSETTA(1999):"Yes",1:"No")
No```

## Nanoquery

Translation of: Python

<lang Nanoquery>def isLeapYear(year) if (year % 100 = 0) return (year % 400 = 0) else return (year % 4 = 0) end end</lang>

## Neko

Translating from C

<lang ActionScript>/**

<doc>

## Leap year, in Neko

</doc>

• /

var leapyear = function(y) return (\$not(y % 4) && \$istrue(y % 100) || \$not(y % 400))

var tests = \$array(2000, 1997, 1996, 1994, 1990, 1980, 1900) var cnt = \$asize(tests) while (cnt -= 1) >= 0 \$print(tests[cnt], if leapyear(tests[cnt]) " is" else " is not", " a leapyear", "\n")</lang>

Output:
```prompt\$ nekoc leapyear.neko
prompt\$ neko leapyear.n
1900 is not a leapyear
1980 is a leapyear
1990 is not a leapyear
1994 is not a leapyear
1996 is a leapyear
1997 is not a leapyear
2000 is a leapyear```

## Nemerle

Demonstrating implementation as well as use of standard library function. <lang Nemerle>using System; using System.Console; using Nemerle.Assertions; using Nemerle.Imperative;

module LeapYear {

```   IsLeapYear(year : int) : bool
requires year >= 1582 otherwise throw ArgumentOutOfRangeException("year must be in Gregorian calendar.")
// without the contract enforcement would work for proleptic Gregorian Calendar
// in that case we might still want to require year > 0
{
when (year % 400 == 0) return true;
when (year % 100 == 0) return false;
when (year % 4   == 0) return true;
false

```
```   }

Main() : void
{
WriteLine("2000 is a leap year: {0}", IsLeapYear(2000));
WriteLine("2100 is a leap year: {0}", IsLeapYear(2100));
try {
WriteLine("1500 is a leap year: {0}", IsLeapYear(1500));
}
catch {
|e is ArgumentOutOfRangeException => WriteLine(e.Message)
}
WriteLine("1500 is a leap year: {0}", DateTime.IsLeapYear(1500)); // is false, indicating use of proleptic
// Gregorian calendar rather than reverting to
// Julian calendar
WriteLine("{0} is a leap year: {1}", DateTime.Now.Year,
DateTime.IsLeapYear(DateTime.Now.Year));
}
```

}</lang>

Output:
```2000 is a leap year: True
2100 is a leap year: False
Specified argument was out of the range of valid values.
Parameter name: year must be in Gregorian calendar.
1500 is a leap year: False
2013 is a leap year: False```

## NetRexx

Demonstrates both a Gregorian/proleptic Gregorian calendar leap-year algorithm and use of the Java library's `GregorianCalendar` object to determine which years are leap-years.

Note that the Java library indicates that the year 1500 is a leap-year as the Gregorian calendar wasn't established until 1582. The Java library implements the Julian calendar for dates prior to the Gregorian cut-over and leap-year rules in the Julian calendar are different to those for the Gregorian calendar. <lang NetRexx>/* NetRexx */

options replace format comments java crossref savelog symbols nobinary

years = '1500 1580 1581 1582 1583 1584 1600 1700 1800 1900 1994 1996 1997 2000 2004 2008 2009 2010 2011 2012 2100 2200 2300 2400 2500 2600' years['l-a'] = years['n-a'] = years['l-j'] = years['n-j'] =

loop y_ = 1 to years.words

``` year = years.word(y_)
if isLeapyear(year) then years['l-a'] = years['l-a'] year
else years['n-a'] = years['n-a'] year
if GregorianCalendar().isLeapYear(year) then years['l-j'] = years['l-j'] year
else years['n-j'] = years['n-j'] year
end y_
```

years['l-a'] = years['l-a'].strip years['n-a'] = years['n-a'].strip years['l-j'] = years['l-j'].strip years['n-j'] = years['n-j'].strip

say ' Sample years:' years['all'].changestr(' ', ',') say ' Leap years (algorithmically):' years['l-a'].changestr(' ', ',') say ' Leap years (Java library)  :' years['l-j'].changestr(' ', ',') say ' Non-leap years (algorithmically):' years['n-a'].changestr(' ', ',') say ' Non-leap years (Java library)  :' years['n-j'].changestr(' ', ',')

return

-- algorithmically method isLeapyear(year = int) public constant binary returns boolean

``` select
when year // 400 = 0 then ly = isTrue
when year // 100 \= 0 & year // 4 = 0 then ly = isTrue
otherwise ly = isFalse
end
return ly
```

method isTrue public constant binary returns boolean

``` return 1 == 1
```

method isFalse public constant binary returns boolean

``` return \isTrue</lang>
```
Output:
``` Sample years: 1500,1580,1581,1582,1583,1584,1600,1700,1800,1900,1994,1996,1997,2000,2004,2008,2009,2010,2011,2012,2100,2200,2300,2400,2500,2600
Leap years (algorithmically): 1580,1584,1600,1996,2000,2004,2008,2012,2400
Leap years (Java library)   : 1500,1580,1584,1600,1996,2000,2004,2008,2012,2400
Non-leap years (algorithmically): 1500,1581,1582,1583,1700,1800,1900,1994,1997,2009,2010,2011,2100,2200,2300,2500,2600
Non-leap years (Java library)   : 1581,1582,1583,1700,1800,1900,1994,1997,2009,2010,2011,2100,2200,2300,2500,2600
```

## Nim

<lang nim>import times let year = 1980 echo isLeapYear(year)

1. or

proc isLeapYear2(year: Natural): bool =

``` if year mod 100 == 0:
year mod 400 == 0
else: year mod 4 == 0
```

echo isLeapYear2(year)</lang>

Output:
```true
true```

## NS-HUBASIC

<lang NS-HUBASIC>10 INPUT "ENTER A NUMBER, AND I'LL DETECT IF IT'S A LEAP YEAR OR NOT. ",A 20 IF A-(A/100)*100=0 AND A-(A/400)*400<>0 THEN RESULT\$="NOT " 30 PRINT "THAT'S "RESULT\$"A LEAP YEAR."</lang>

## Oberon-2

<lang oberon2> PROCEDURE IsLeapYear(year: INTEGER): BOOLEAN; BEGIN

``` IF year MOD 4 # 0 THEN
RETURN FALSE
ELSE
IF year MOD 100 = 0 THEN
IF year MOD 400  = 0 THEN
```

RETURN TRUE

```     ELSE
```

RETURN FALSE

```     END
ELSE
RETURN TRUE
END
END
```

END IsLeapYear; </lang>

## Objeck

<lang objeck>bundle Default {

``` class LeapYear {
function : Main(args : String[]) ~ Nil {
test_case := [1900, 1994, 1996, 1997, 2000];
each(i : test_case) {
test_case[i]->Print();
if(IsLeapYear(test_case[i])) {
" is a leap year."->PrintLine();
}
else {
" is not a leap year."->PrintLine();
};
};
}
```
```   function : native : IsLeapYear(year : Int) ~ Bool {
if(year % 4 = 0 & year % 100 <> 0) {
return true;
}
else if(year % 400 = 0) {
return true;
};
```
```     return false;
}
}
```

}</lang>

## OCaml

<lang ocaml>let is_leap_year ~year =

``` if (year mod 100) = 0
then (year mod 400) = 0
else (year mod 4) = 0</lang>
```

Using Unix Time functions: <lang ocaml>let is_leap_year ~year =

``` let tm =
Unix.mktime {
(Unix.gmtime (Unix.time())) with
Unix.tm_year = (year - 1900);
tm_mon = 1 (* feb *);
tm_mday = 29
}
in
(tm.Unix.tm_mday = 29)</lang>
```

## Oforth

<lang Oforth>Date.IsLeapYear(2000)</lang>

## ooRexx

<lang ooRexx>

routine isLeapYear
``` use arg year
d = .datetime~new(year, 1, 1)
return d~isLeapYear
```

</lang>

## OpenEdge/Progress

The DATE function converts month, day, year integers to a date data type and will set the error status if invalid values are passed. <lang progress>FUNCTION isLeapYear RETURNS LOGICAL (

```  i_iyear AS INTEGER
```

):

```  DATE( 2, 29, i_iyear ) NO-ERROR.
RETURN NOT ERROR-STATUS:ERROR.
```

END FUNCTION. /* isLeapYear */

MESSAGE

```  1900 isLeapYear( 1900 ) SKIP
1994 isLeapYear( 1994 ) SKIP
1996 isLeapYear( 1996 ) SKIP
1997 isLeapYear( 1997 ) SKIP
2000 isLeapYear( 2000 )
```

## Oz

<lang oz>declare

``` fun {IsLeapYear Year}
case Year mod 100 of 0 then
```

Year mod 400 == 0

```    else
```

Year mod 4 == 0

```    end
end
```

in

``` for Y in [1900 1996 1997 2000] do
if {IsLeapYear Y} then
```

{System.showInfo Y#" is a leap year."}

```    else
```

{System.showInfo Y#" is NOT a leap year."}

```    end
end</lang>
```
Output:
```1900 is NOT a leap year.
1996 is a leap year.
1997 is NOT a leap year.
2000 is a leap year.```

## PARI/GP

<lang parigp>isLeap(n)={

``` if(n%400==0, return(1));
if(n%100==0, return(0));
n%4==0
```

};</lang>

Alternate version: <lang parigp>isLeap(n)=!(n%if(n%100,4,400))</lang>

Works with: PARI/GP version 2.6.0 and above

<lang parigp>isLeap(n)={

``` if(n%4,0,
n%100,1,
n%400,0,1
)
```

};</lang>

## Pascal

Works with: Free Pascal

<lang pascal>program LeapYear; uses

``` sysutils;//includes isLeapYear

```

procedure TestYear(y: word); begin

``` if IsLeapYear(y) then
writeln(y,' is a leap year')
else
writeln(y,' is NO leap year');
```

end; Begin

``` TestYear(1900);
TestYear(2000);
TestYear(2100);
TestYear(1904);
```

end.</lang> Output:

```1900 is NO leap year
2000 is a leap year
2100 is NO leap year
1904 is a leap year```

## Perl

<lang Perl>sub isleap {

```   my \$year = shift;
if (\$year % 100 == 0) {
return (\$year % 400 == 0);
}
return (\$year % 4 == 0);
```

}</lang>

Or more concisely:

<lang Perl>sub isleap { !(\$_[0] % 100) ? !(\$_[0] % 400) : !(\$_[0] % 4) }</lang>

Alternatively, using functions/methods from CPAN modules:

<lang Perl>use Date::Manip; print Date_LeapYear(2000);

use Date::Manip::Base; my \$dmb = new Date::Manip::Base; print \$dmb->leapyear(2000);

use DateTime; my \$date = DateTime->new(year => 2000); print \$date->is_leap_year();</lang>

## Phix

Available as an auto-include, implemented as:

```global function is_leap_year(integer y)
return remainder(y,4)=0 and (remainder(y,100)!=0 or remainder(y,400)=0)
end function
```

## PHP

<lang php><?php function isLeapYear(\$year) {

```   if (\$year % 100 == 0) {
return (\$year % 400 == 0);
}
return (\$year % 4 == 0);
```

}</lang> With `date('L')`: <lang php><?php function isLeapYear(\$year) {

```   return (date('L', mktime(0, 0, 0, 2, 1, \$year)) === '1')
```

}</lang>

## PicoLisp

<lang PicoLisp>(de isLeapYear (Y)

```  (bool (date Y 2 29)) )</lang>
```
Output:
```: (isLeapYear 2010)
-> NIL

: (isLeapYear 2008)
-> T

: (isLeapYear 1600)
-> T

: (isLeapYear 1700)
-> NIL```

## PL/I

<lang pli>dcl mod builtin; dcl year fixed bin (31);

do year = 1900, 1996 to 2001;

``` if mod(year, 4)    = 0 &
(mod(year, 100) ^= 0 |
mod(year, 400)  = 0) then
put skip edit(year, 'is a leap year') (p'9999b', a);
else
put skip edit(year, 'is not a leap year') (p'9999b', a);
```

end;</lang>

Output:
```1900 is not a leap year
1996 is a leap year
1997 is not a leap year
1998 is not a leap year
1999 is not a leap year
2000 is a leap year
2001 is not a leap year
```

## PostScript

<lang postscript>/isleapyear {

```   dup dup
4 mod 0 eq     % needs to be divisible by 4
exch
100 mod 0 ne   % but not by 100
and
exch
400 mod 0 eq   % or by 400
or
```

} def</lang>

## PowerShell

<lang powershell>\$Year = 2016 [System.DateTime]::IsLeapYear( \$Year )</lang>

## Prolog

Works with: SWI-Prolog

<lang Prolog>leap_year(L) :- partition(is_leap_year, L, LIn, LOut), format('leap years : ~w~n', [LIn]), format('not leap years : ~w~n', [LOut]).

is_leap_year(Year) :- R4 is Year mod 4, R100 is Year mod 100, R400 is Year mod 400, ( (R4 = 0, R100 \= 0); R400 = 0).</lang>

Output:

<lang Prolog> ?- leap_year([1900,1994,1996,1997,2000 ]). leap years : [1996,2000] not leap years : [1900,1994,1997] L = [1900,1994,1996,1997,2000].</lang>

There is an handy builtin that simplifies a lot, ending up in a simple query:

<lang Prolog> ?- findall(Y, (between(1990,2030,Y),day_of_the_year(date(Y,12,31),366)), L). L = [1992, 1996, 2000, 2004, 2008, 2012, 2016, 2020, 2024, 2028]. </lang>

## PureBasic

<lang PureBasic>Procedure isLeapYear(Year)

``` If (Year%4=0 And Year%100) Or Year%400=0
ProcedureReturn #True
Else
ProcedureReturn #False
EndIf
```

EndProcedure</lang>

## Python

<lang python>import calendar calendar.isleap(year)</lang> or <lang python>def is_leap_year(year):

```   if year % 100 == 0:
return year % 400 == 0
return year % 4 == 0</lang>
```

def is_leap_year(year):

```   try:
datetime.date(year, 2, 29)
except ValueError:
return False
return True</lang>
```

## Q

<lang q>ly:{((0<>x mod 100) | 0=x mod 400) & 0=x mod 4} / Return 1b if x is a leap year; 0b otherwise</lang>

## Quackery

Translation of: Forth

<lang Quackery> [ dup 400 mod 0 = iff [ drop true ] done

```   dup 100 mod 0 = iff [ drop false ] done
4 mod 0 = ]                       is leap? ( n --> b )</lang>
```

## R

<lang R>isLeapYear <- function(year) {

```   ifelse(year%%100==0, year%%400==0, year%%4==0)
```

}

for (y in c(1900, 1994, 1996, 1997, 2000)) {

``` cat(y, ifelse(isLeapYear(y), "is", "isn't"), "a leap year.\n")
```

}</lang>

Output:
```1900 isn't a leap year.
1994 isn't a leap year.
1996 is a leap year.
1997 isn't a leap year.
2000 is a leap year.
```

## Racket

<lang racket>(define (leap-year? y)

``` (and (zero? (modulo y 4)) (or (positive? (modulo y 100)) (zero? (modulo y 400)))))</lang>
```

## Raku

(formerly Perl 6)

Works with: Rakudo version 2010.07

<lang perl6>say "\$year is a {Date.is-leap-year(\$year) ?? 'leap' !! 'common'} year."</lang> In Rakudo 2010.07, `Date.is-leap-year` is implemented as <lang perl6>multi method is-leap-year(\$y = \$!year) {

```   \$y %% 4 and not \$y %% 100 or \$y %% 400
```

}</lang>

## Raven

<lang Raven>define is_leap_year use \$year

```   \$year 100 % 0 = if
\$year 400 % 0 =
\$year 4 % 0 =</lang>
```

## REBOL

<lang rebol>leap-year?: func [

```   {Returns true if the specified year is a leap year; false otherwise.}
year [date! integer!]
/local div?
```

][

```   either date? year [year: year/year] [
if negative? year [throw make error! join [script invalid-arg] year]
]
; The key numbers are 4, 100, and 400, combined as follows:
;   1) If the year is divisible by 4, it’s a leap year.
;   2) But, if the year is also divisible by 100, it’s not a leap year.
;   3) Double but, if the year is also divisible by 400, it is a leap year.
div?: func [n] [zero? year // n]
to logic! any [all [div? 4  not div? 100] div? 400]
```

]</lang>

## Retro

<lang Retro>:isLeapYear? (y-f)

```   dup #400 mod n:zero? [ drop #-1 #0 ] [ #1 ] choose 0; drop
dup #100 mod n:zero? [ drop  #0 #0 ] [ #1 ] choose 0; drop
#4 mod n:zero? ;</lang>
```

## REXX

### local variables

<lang rexx>leapyear: procedure; parse arg yr return yr//400==0 | (yr//100\==0 & yr//4==0)</lang>

### with short-circuit

The REXX language doesn't support short-circuits, so here is a version that does a short-circuit. <lang rexx>leapyear: procedure; parse arg yr if yr//4\==0 then return 0 /*Not ÷ by 4? Not a leap year.*/ return yr//400==0 | yr//100\==0</lang>

### no local variables

This version doesn't need a PROCEDURE to hide local variable(s)   [because there aren't any local variables],
but it does invoke the   ARG   BIF multiple times. <lang rexx>leapyear: if arg(1)//4\==0 then return 0

```         return arg(1)//400==0  |  arg(1)//100\==0</lang>
```

### handles 2 digit year

This REXX version has the proviso that if the year is exactly two digits,
the current century is assumed   (i.e.,   no year windowing).

If a year below 100 is to be used, the year should have leading zeroes added (to make it four digits). <lang rexx>leapyear: procedure; parse arg y /*year could be: Y, YY, YYY, YYYY*/ if y//4\==0 then return 0 /*Not ÷ by 4? Not a leap year.*/ if length(y)==2 then y=left(date('S'),2)y /*adjust for a 2─digit YY year.*/ return y//100\==0 | y//400==0 /*apply 100 and 400 year rule. */</lang>

## Ring

<lang ring> give year leap = isLeapYear(year) if leap true see year + " is leap year." else see year + " is not leap year." ok

Func isLeapYear year

```    if (year % 400) = 0 return true
but (year % 100) = 0 return false
but (year % 4) = 0 return true
else return false ok
```

</lang>

## RPG

Works with: RPGIII

```    C           *ENTRY    PLIST
C                     PARM           YEAR    40       input (year)
C                     PARM           ISLEAP  1        output (Y/N)
C*
C                     MOVE 'N'       ISLEAP
C           YEAR      CABLE1752      DONE             not Gregorian
C*
C           YEAR      DIV  4         RESULT  40
C                     MVR            REMAIN  40
C           REMAIN    CABNE0         DONE
C*
C* If we got here, year is divisible by 4.
C           YEAR      DIV  100       RESULT
C                     MVR            REMAIN
C           REMAIN    CABNE0         LEAPYR
C*
C* If we got here, year is divisible by 100.
C           YEAR      DIV  400       RESULT
C                     MVR            REMAIN
C           REMAIN    CABNE0         DONE
C*
C           LEAPYR    TAG
C                     MOVE 'Y'       ISLEAP
C*
C           DONE      TAG
C                     SETON                     LR</lang>
```

## Ruby

<lang ruby>require 'date'

Date.leap?(year)</lang>

The leap? method is aliased as gregorian_leap? And yes, there is a julian_leap? method.

## Run BASIC

<lang runbasic>if date\$("02/29/" + mid\$(date\$("mm/dd/yyyy"),7,4)) then print "leap year" else print "not"</lang>

## Rust

<lang rust>fn is_leap(year: i32) -> bool {

```   let factor = |x| year % x == 0;
factor(4) && (!factor(100) || factor(400))
```

}</lang>

## S-BASIC

Since S-BASIC has no MOD operator or function, we have to supply one. <lang basic> rem - compute p mod q function mod(p, q = integer) = integer end = p - q * (p/q)

rem - return true (-1) if y is a leap year, otherwise 0 function isleapyear(y = integer) = integer end = mod(y,4)=0 and mod(y,100)<>0 or mod(y,400)=0

rem - exercise the function var y = integer

print "Test of century years" for y = 1600 to 2000 step 100

```  if isleapyear(y) then
print y;" is a leap year"
else
print y;" is NOT a leap year"
```

next y

print "Test of current half-decade" for y = 2015 to 2020

```  if isleapyear(y) then
print y; " is a leap year"
else
print y; " is NOT a leap year"
```

next y

end </lang>

Output:
```Test of century years
1600 is a leap year
1700 is NOT a leap year
1800 is NOT a leap year
1900 is NOT a leap year
2000 is a leap year
2015 is NOT a leap year
2016 is a leap year
2017 is NOT a leap year
2018 is NOT a leap year
2019 is NOT a leap year
2020 is a leap year
```

## Scala

### JDK 7 (not recommended)

By default, java.util.GregorianCalendar switches from Julian calendar to Gregorian calendar at 15 October 1582.

<lang scala>//use Java's calendar class new java.util.GregorianCalendar().isLeapYear(year)</lang>

### JDK 8

Using JSR-310 java.time. <lang scala>java.time.LocalDate.ofYearDay(year, 1).isLeapYear()</lang>

### Implementation

For proleptic Gregorian calendar:

<lang scala>def isLeapYear(year:Int)=if (year%100==0) year%400==0 else year%4==0;

//or use Java's calendar class def isLeapYear(year:Int):Boolean = {

``` val c = new java.util.GregorianCalendar
c.setGregorianChange(new java.util.Date(Long.MinValue))
c.isLeapYear(year)
```

}</lang>

## Scheme

<lang scheme>(define (leap-year? n) (apply (lambda (a b c) (or a (and (not b) c)))

```      (map (lambda (m) (zero? (remainder n m)))
'(400 100 4))))</lang>
```

## Seed7

This function is part of the "time.s7i" library. It returns TRUE if the year is a leap year in the Gregorian calendar. <lang seed7>const func boolean: isLeapYear (in integer: year) is

``` return (year rem 4 = 0 and year rem 100 <> 0) or year rem 400 = 0;</lang>
```

Original source: [1]

## Sidef

<lang ruby>func isleap(year) {

```   if (year %% 100) {
return (year %% 400);
}
return (year %% 4);
```

}</lang>

or a little bit simpler: <lang ruby>func isleap(year) { year %% 100 ? (year %% 400) : (year %% 4) };</lang>

## Smalltalk

Smalltalk has a built-in method named isLeapYear: <lang smalltalk> Date today isLeapYear. </lang>

## SNOBOL4

Predicate leap( ) succeeds/fails, returns nil. <lang SNOBOL4> define('leap(yr)')  :(end_leap) leap eq(remdr(yr,400),0) :s(return)

```       eq(remdr(yr,100),0) :s(freturn)
eq(remdr(yr,4),0)   :s(return)f(freturn)
```

end_leap

• # Test and display (with ?: kluge)
```       test = "output = ('10' ? (*leap(yr) 1 | 0)) ': ' yr"
yr = '1066'; eval(test)
yr = '1492'; eval(test)
yr = '1900'; eval(test)
yr = '2000'; eval(test)
```

end</lang>

Output:
```0: 1066
1: 1492
0: 1900
1: 2000```

## Standard ML

<lang sml>fun isLeapYear y =

``` y mod (if y mod 100 = 0 then 400 else 4) = 0</lang>
```

## Stata

Given a dataset with a "year" variable, generate a variable "leap" which is 1 for a leap year, 0 otherwise.

<lang stata>gen leap = mod(year,400)==0 | mod(year,4)==0 & mod(year,100)!=0</lang>

See also the article How do I identify leap years in Stata? by Nicholas J. Cox in Stata FAQ.

## Swift

<lang Swift>func isLeapYear(year:Int) -> Bool {

```  return (year % 100 == 0) ? (year % 400 == 0) : (year % 4 == 0)
```

}

print(isLeapYear(2000)) print(isLeapYear(2011))</lang>

Output:
```true
false
```

## Tcl

The "classic" modulo comparison: <lang tcl>proc isleap1 {year} {

```   return [expr {(\$year % 4 == 0) && ((\$year % 100 != 0) || (\$year % 400 == 0))}]
```

} isleap1 1988 ;# => 1 isleap1 1989 ;# => 0 isleap1 1900 ;# => 0 isleap1 2000 ;# => 1</lang> Does Feb 29 exist in the given year? If not a leap year, the clock command will return "03-01". (This code will switch to the Julian calendar for years before 1582.) <lang tcl>proc isleap2 year {

```   return [expr {[clock format [clock scan "\$year-02-29" -format "%Y-%m-%d"] -format "%m-%d"] eq "02-29"}]
```

} isleap2 1988 ;# => 1 isleap2 1989 ;# => 0 isleap2 1900 ;# => 0 isleap2 2000 ;# => 1</lang>

## TUSCRIPT

<lang tuscript>\$\$ MODE TUSCRIPT LOOP year="1900'1994'1996'1997'2000",txt="" SET dayoftheweek=DATE(number,29,2,year,number) IF (dayoftheweek==0) SET txt="not " PRINT year," is ",txt,"a leap year" ENDLOOP</lang>

Output:
```1900 is not a leap year
1994 is not a leap year
1996 is a leap year
1997 is not a leap year
2000 is a leap year
```

## uBasic/4tH

Translation of: BBC BASIC

<lang>DO

``` INPUT "Enter a year: "; y
IF FUNC(_FNleap(y)) THEN
PRINT y; " is a leap year"
ELSE
PRINT y; " is not a leap year"
ENDIF
```

LOOP END

_FNleap Param (1) RETURN ((a@ % 4 = 0) * ((a@ % 400 = 0) + (a@ % 100 # 0)))</lang>

## UNIX Shell

Original Bourne: <lang sh>leap() {

``` if expr \$1 % 4 >/dev/null; then return 1; fi
if expr \$1 % 100 >/dev/null; then return 0; fi
if expr \$1 % 400 >/dev/null; then return 1; fi
return 0;
```

}</lang>

Using GNU date(1): <lang sh>leap() {

``` date -d "\$1-02-29" >/dev/null 2>&1;
```

}</lang>

Defining a bash function is_leap which accepts a YEAR argument, and uses no IO redirection, nor any extra processes. <lang sh>is_leap() {

``` local year=\$(( 10#\${1:?'Missing year'} ))
(( year % 4 == 0 && ( year % 100 != 0 || year % 400 == 0 ) )) && return 0
return 1
```

}</lang>

Using the cal command: (note that this invokes two processes with IO piped between them and is relatively heavyweight compared to the above shell functions: leap and is_leap) <lang sh>leap() {

``` cal 02 \$1 | grep -q 29
```

} </lang>

## Ursa

This program takes a year as a command line argument. <lang ursa>decl int year set year (int args<1>) if (= (mod year 4) 0)

```       if (and (= (mod year 100) 0) (not (= (mod year 400) 0)))
out year " is not a leap year" endl console
else
out year " is a leap year" endl  console
end if
```

else

```       out year " is not a leap year" endl console
```

end if</lang> Output in Bash:

```\$ ursa leapyear.u 1900
1900 is not a leap year
\$ ursa leapyear.u 2000
2000 is a leap year```

## Vala

<lang Vala>void main() {

``` DateYear[] years = { 1900, 1994, 1996, 1997, 2000 };
foreach ( DateYear year in years ) {
string status = year.is_leap_year() ? "" : "not ";
print (@"\$year is \$(status)a leap year.\n");
}
```

}</lang>

Output:
```1900 is not a leap year.
1994 is not a leap year.
1996 is a leap year.
1997 is not a leap year.
2000 is a leap year.
```

## VBA

<lang vb>Public Function Leap_year(year As Integer) As Boolean

```   Leap_year = (Month(DateSerial(year, 2, 29)) = 2)
```

End Function</lang>

## VBScript

<lang vb> Function IsLeapYear(yr) IsLeapYear = False If yr Mod 4 = 0 And (yr Mod 400 = 0 Or yr Mod 100 <> 0) Then IsLeapYear = True End If End Function

'Testing the function. arr_yr = Array(1900,1972,1997,2000,2001,2004)

For Each yr In arr_yr If IsLeapYear(yr) Then WScript.StdOut.WriteLine yr & " is leap year." Else WScript.StdOut.WriteLine yr & " is NOT leap year." End If Next </lang>

Output:
```1900 is NOT leap year.
1972 is leap year.
1997 is NOT leap year.
2000 is leap year.
2001 is NOT leap year.
2004 is leap year.
```

## Vedit macro language

<lang vedit>while (#1 = Get_Num("Year: ")) {

```   #2 = (#1 % 4 == 0) && ((#1 % 100 != 0) || (#1 % 400 == 0))
if (#2) {
Message(" is leap year\n")
} else {
```

Message(" is not leap year\n")

```   }
```

}</lang>

The following version requires Vedit 6.10 or later: <lang vedit>while (#1 = Get_Num("Year: ")) {

```   if (Is_Leap_Year(#1)) {
Message(" is leap year\n")
} else {
```

Message(" is not leap year\n")

```   }
```

}</lang>

## Visual Basic

Works with: Visual Basic version VB6 Standard

<lang vb> Public Function IsLeapYear1(ByVal theYear As Integer) As Boolean 'this function utilizes documented behaviour of the built-in DateSerial function IsLeapYear1 = (VBA.Day(VBA.DateSerial(theYear, 2, 29)) = 29) End Function

Public Function IsLeapYear2(ByVal theYear As Integer) As Boolean 'this function uses the well-known formula IsLeapYear2 = IIf(theYear Mod 100 = 0, theYear Mod 400 = 0, theYear Mod 4 = 0) End Function </lang> Testing: <lang vb> Sub Main() 'testing the above functions Dim i As Integer

``` For i = 1750 To 2150
Debug.Assert IsLeapYear1(i) Eqv IsLeapYear2(i)
Next i
```

End Sub </lang>

## Visual Basic .NET

Translation of: C#

<lang vbnet>Module Module1

```   Sub Main()
For Each y In {1900, 1994, 1996, Date.Now.Year}
Console.WriteLine("{0} is {1}a leap year.", y, If(Date.IsLeapYear(y), String.Empty, "not "))
Next
End Sub
```

End Module</lang>

Output:
```1900 is not a leap year.
1994 is not a leap year.
1996 is a leap year.
2019 is not a leap year.```

## WDTE

<lang WDTE>let str => import 'strings';

let multiple of n => == (% n of) 0;

let leap year => str.format '{} is{} a leap year.' year (switch year {

``` multiple 400 => ;
multiple 100 => ' not';
multiple 4 => ;
default => ' not';
```

}) -- io.writeln io.stdout;</lang>

## Wortel

<lang wortel>@let {

``` isLeapYear !?{\~%%1H \~%%4H \~%%4}
!-isLeapYear @range[1900 2000]
```

}</lang> Returns:

`[1904 1908 1912 1916 1920 1924 1928 1932 1936 1940 1944 1948 1952 1956 1960 1964 1968 1972 1976 1980 1984 1988 1992 1996 2000]`

## Wren

<lang ecmascript>var isLeapYear = Fn.new { |y|

```   return ((y % 4 == 0) && (y % 100!= 0)) || (y % 400 == 0)
```

}

System.print("Leap years between 1900 and 2020 inclusive:") var c = 0 for (i in 1900..2020) {

```   if (isLeapYear.call(i)) {
System.write("%(i) ")
c = c + 1
if (c % 15 == 0) System.print()
}
```

}</lang>

Output:
```Leap years between 1900 and 2020 inclusive:
1904 1908 1912 1916 1920 1924 1928 1932 1936 1940 1944 1948 1952 1956 1960
1964 1968 1972 1976 1980 1984 1988 1992 1996 2000 2004 2008 2012 2016 2020
```

## X86 Assembly

Using FASM syntax. Leaf function fits nicely into your program. <lang asm> align 16

Input year as signed dword in EAX

IsLeapYear:

```   test eax,11b
jz .4
retn ; 75% : ZF=0, not a leap year
```

.4:

```   mov ecx,100
cdq
idiv ecx
test edx,edx
jz .100
cmp edx,edx
retn ; 24% : ZF=1, leap year
```

.100:

```   test eax,11b
retn ; 1% : ZF=?, leap year if EAX%400=0</lang>
```

## XLISP

<lang xlisp>(DEFUN LEAP-YEARP (YEAR)

```   (AND (= (MOD YEAR 4) 0) (OR (/= (MOD YEAR 100) 0) (= (MOD YEAR 400) 0))))
```
Test the function

(DISPLAY (MAPCAR LEAP-YEARP '(1600 1640 1800 1928 1979 1990 2000 2004 2005 2016)))</lang>

Output:
`(#T #T () #T () () #T #T () #T)`

## XPL0

<lang XPL0>func LeapYear(Y); \Return 'true' if Y is a leap year int Y; [if rem(Y/100)=0 then return rem(Y/400)=0; return rem(Y/4)=0; ];</lang>

## Yorick

This solution is vectorized and can be applied to scalar or array input. <lang yorick>func is_leap(y) {

``` return ((y % 4 == 0) & (y % 100 != 0)) | (y % 400 == 0);
```

}</lang> Interactive example usage:

```> is_leap(1988)
1
> is_leap([1988,1989,1900,2000])
[1,0,0,1]```

## zkl

<lang zkl>Time.Date.isLeapYear(1988) //-->True T(1988,1989,1900,2000).apply(Time.Date.isLeapYear)

```   //-->L(True,False,False,True)</lang>
```