Days between dates: Difference between revisions
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Days between 2090-01-01 and 2098-12-25 is 3280 days
</pre>
=={{header|Frink}}==
Line 1,268 ⟶ 1,267:
{{FormulaeEntry|page=https://formulae.org/?timeZone=America%2FLos_Angeles&script=examples/Days_between_dates}}
'''Solution'''
Note. For this script, the time zone is intentionally set to America/Los_Angeles, because it observes [https://en.wikipedia.org/wiki/Daylight_saving_time daylight saving time], It is necesary to solve this exercise.
Provided that the ToNumber expression applied to a time expression reduces to the number of milliseconds of such that time from the [https://en.wikipedia.org/wiki/Epoch_(computing) epoch]:
[[File:Fōrmulæ - Days between dates 01.png]]
[[File:Fōrmulæ - Days between dates 02.png]]
The solution seems easy, calculating the difference between two times (in milliseconds), and dividing by 86,4000,000 (number of milliseconds in a day):
[[File:Fōrmulæ - Days between dates 03.png]]
[[File:Fōrmulæ - Days between dates 04.png]]
However, it does not work if one time is in daylight saving time, and the other one is in standard time:
[[File:Fōrmulæ - Days between dates 05.png]]
[[File:Fōrmulæ - Days between dates 06.png]]
[[File:Fōrmulæ - Days between dates 07.png]]
[[File:Fōrmulæ - Days between dates 08.png]]
'''Solution 1'''
The first solution consists in simply rounding the result to the nearest integer:
[[File:Fōrmulæ - Days between dates 09.png]]
[[File:Fōrmulæ - Days between dates 10.png]]
'''Solution 2'''
The expression GetTimeZoneOffset reduces to the offset (in minutes) of the given time.
[[File:Fōrmulæ - Days between dates 11.png]]
[[File:Fōrmulæ - Days between dates 12.png]]
[[File:Fōrmulæ - Days between dates 13.png]]
[[File:Fōrmulæ - Days between dates 14.png]]
The solution consist in taking this difference in account.
So, the function that works correctly is:
[[File:Fōrmulæ - Days between dates 15.png]]
'''Test cases'''
[[File:Fōrmulæ - Days between dates 16.png]]
[[File:Fōrmulæ - Days between dates 17.png]]
Notice that it works even for fractions of days:
[[File:Fōrmulæ - Days between dates 18.png]]
[[File:Fōrmulæ - Days between dates 19.png]]
=={{header|Go}}==
Line 1,661 ⟶ 1,724:
Days between 1902-01-01 and 1968-12-25: 24465
Days between 2090-01-01 and 2098-12-25: 3280</pre>
=={{header|Pascal}}==
==={{header|Free Pascal}}===
<syntaxhighlight lang="pascal">
Program DaysBetweenDates;
{$mode ObjFPC}{$H+}
Uses dateutils,strutils;
Type Tarr = array of array Of string;
Const lst : Tarr = (('1902-01-01','1968-12-25'),('2019-01-01','2019-01-02'),
('2019-01-02','2019-01-01'),('2019-01-01','2019-03-01'),
('2020-01-01','2020-03-01'),('1995-11-21','1995-11-21'),
('2090-01-01','2098-12-25'),('1967-02-23','2024-03-21'));
Function strtodate(str : String) : tdatetime;
Begin
result := ScanDateTime('YYYYMMDD', DelChars(str, '-'));
End;
Var arr : array of string;
DaysBetw : integer;
Begin
For arr In lst Do
Begin
DaysBetw := DaysBetween(strtodate(arr[0]),strtodate(arr[1]));
writeln(arr[0],' - ',arr[1],' -> ',DaysBetw);
End;
End.
</syntaxhighlight>
{{out}}
<pre>
1902-01-01 - 1968-12-25 -> 24465
2019-01-01 - 2019-01-02 -> 1
2019-01-02 - 2019-01-01 -> 1
2019-01-01 - 2019-03-01 -> 59
2020-01-01 - 2020-03-01 -> 60
1995-11-21 - 1995-11-21 -> 0
2090-01-01 - 2098-12-25 -> 3280
1967-02-23 - 2024-03-21 -> 20846
</pre>
=={{header|Perl}}==
Line 1,730 ⟶ 1,835:
</pre>
=={{header|PL/I-80}}==
{{Trans|S-BASIC}}
<syntaxhighlight lang = "PL/I">
elapsed_days: proc options (main);
dcl
(date1, date2) float bin,
another char(1);
put skip list ('Elapsed days calculator');
another = 'Y';
do while ((another = 'Y') | (another = 'y'));
put skip list ('First date as YYYY-MM-DD : ');
date1 = get_date();
put list ('Second date as YYYY-MM-DD : ');
date2 = get_date();
put skip edit ('Elapsed days = ', date2-date1) (a,f(6));
put skip list ('Do another (y/n)? ');
get edit (another) (a);
end;
/*
* Read a date in YYYY-MM-DD format from the
* console and return its serial date equivalent
*/
get_date: proc returns (float bin);
dcl date char(20) varying;
dcl (y, m, d) float bin;
get edit (date) (a);
y = binary(substr(date,1,4));
m = binary(substr(date,6,2));
d = binary(substr(date,9,2));
return (serial_date(y,m,d));
end get_date;
/*
* Given a year, month and day in the Gregorian
* calendar, return a numeric date which is equal
* to the number of days since the start of the
* Common era
*/
serial_date: proc (yr, mo, da) returns (float bin);
dcl (yr, mo, da) float bin;
dcl n float bin;
n = 365 * yr + da + 31 * (mo - 1);
if (mo >= 3) then
n = n - fixed(0.4 * mo + 2.3);
else
yr = yr - 1;
n = n + fixed(yr/4) - fixed(0.75 * fixed(yr/100) + 1);
return (n);
end serial_date;
end elapsed_days;
</syntaxhighlight>
{{out}}
Test case taken from the Delphi example
<pre>
Elapsed Date Calculator
First date as YYYY-MM-DD : 1970-01-01
Second date as YYYY-MM-DD : 2019-10-18
Elapsed days = 18187
Do another (y/n)? n
</pre>
=={{header|PL/M}}==
{{Trans|FreeBASIC}}
{{works with|8080 PL/M Compiler}} ... under CP/M (or an emulator)<br>
Note that as the 8080 PL/M compiler only supports 8 and 16 bit unsigned integers, the dates must be at most 65535 days apart.
<syntaxhighlight lang="plm">
100H: /* CALCULATE THE NUMBER OF DAYS BETWEEN TWO DATES; BASED ON FREEBASIC */
/* CP/M BDOS SYSTEM CALL AND I/O ROUTINES */
BDOS: PROCEDURE( FN, ARG ); DECLARE FN BYTE, ARG ADDRESS; GOTO 5; END;
PR$CHAR: PROCEDURE( C ); DECLARE C BYTE; CALL BDOS( 2, C ); END;
PR$STRING: PROCEDURE( S ); DECLARE S ADDRESS; CALL BDOS( 9, S ); END;
PR$NL: PROCEDURE; CALL PR$CHAR( 0DH ); CALL PR$CHAR( 0AH ); END;
PR$NUMBER: PROCEDURE( N ); /* PRINTS A NUMBER IN THE MINIMUN FIELD WIDTH */
DECLARE N ADDRESS;
DECLARE V ADDRESS, N$STR ( 6 )BYTE, W BYTE;
V = N;
W = LAST( N$STR );
N$STR( W ) = '$';
N$STR( W := W - 1 ) = '0' + ( V MOD 10 );
DO WHILE( ( V := V / 10 ) > 0 );
N$STR( W := W - 1 ) = '0' + ( V MOD 10 );
END;
CALL PR$STRING( .N$STR( W ) );
END PR$NUMBER;
PR$SIGNED: PROCEDURE( N ); /* PRINTS N AS A SIGNED INTEGER */
DECLARE N ADDRESS;
IF N <= 32767
THEN CALL PR$NUMBER( N );
ELSE DO;
CALL PR$CHAR( '-' );
CALL PR$NUMBER( - N );
END;
END PR$SIGNED ;
/* TASK */
/* RETURNS THE GREGORIAN DAY CORRESPONDING TO YYYY/MM/DD */
GREGORIAN: PROCEDURE( YYYY$MM$DD )ADDRESS;
DECLARE YYYY$MM$DD ADDRESS;
DECLARE DATE BASED YYYY$MM$DD ( 10 )BYTE;
DECLARE ( YYYY, MM, DD, N, W ) ADDRESS;
DIGIT: PROCEDURE( D )BYTE; DECLARE D BYTE; RETURN D - '0'; END;
YYYY = ( DIGIT( DATE( 0 ) ) * 1000 ) + ( DIGIT( DATE( 1 ) ) * 100 )
+ ( DIGIT( DATE( 2 ) ) * 10 ) + DIGIT( DATE( 3 ) );
MM = ( DIGIT( DATE( 5 ) ) * 10 ) + DIGIT( DATE( 6 ) );
DD = ( DIGIT( DATE( 8 ) ) * 10 ) + DIGIT( DATE( 9 ) );
N = ( MM + 9 ) - ( ( ( MM + 9 ) / 12 ) * 12 );
W = YYYY - ( N / 10 );
RETURN ( 365 * W ) + ( W / 4 ) - ( W / 100 ) + ( W / 400 )
+ ( ( ( N * 306 ) + 5 ) / 10 ) + ( DD - 1 );
END GREGORIAN ;
/* SHOWS TTHE DAYS DIFFERENCE BETWEEN FROM$G AND TO$$G */
PR$DAYS$DIFFERENCE: PROCEDURE( FROM$DATE, TO$DATE );
DECLARE ( FROM$DATE, TO$DATE )ADDRESS;
CALL PR$STRING( .'DAYS BETWEEN $' );CALL PR$STRING( FROM$DATE );
CALL PR$STRING( .' AND $' );CALL PR$STRING( TO$DATE );
CALL PR$STRING( .' IS $' );
CALL PR$SIGNED( GREGORIAN( TO$DATE ) - GREGORIAN( FROM$DATE ) );
CALL PR$NL;
END PR$DAYS$DIFFERENCE ;
CALL PR$DAYS$DIFFERENCE( .'1902-01-01$', .'1968-12-25$' );
CALL PR$DAYS$DIFFERENCE( .'2019-01-01$', .'2019-01-02$' );
CALL PR$DAYS$DIFFERENCE( .'2019-01-02$', .'2019-01-01$' );
CALL PR$DAYS$DIFFERENCE( .'2019-01-01$', .'2019-03-01$' );
CALL PR$DAYS$DIFFERENCE( .'2020-01-01$', .'2020-03-01$' );
CALL PR$DAYS$DIFFERENCE( .'1995-11-21$', .'1995-11-21$' );
CALL PR$DAYS$DIFFERENCE( .'2090-01-01$', .'2098-12-25$' );
EOF
</syntaxhighlight>
{{out}}
<pre>
DAYS BETWEEN 1902-01-01 AND 1968-12-25 IS 24465
DAYS BETWEEN 2019-01-01 AND 2019-01-02 IS 1
DAYS BETWEEN 2019-01-02 AND 2019-01-01 IS -1
DAYS BETWEEN 2019-01-01 AND 2019-03-01 IS 59
DAYS BETWEEN 2020-01-01 AND 2020-03-01 IS 60
DAYS BETWEEN 1995-11-21 AND 1995-11-21 IS 0
DAYS BETWEEN 2090-01-01 AND 2098-12-25 IS 3280
</pre>
=={{header|Python}}==
Line 2,069 ⟶ 2,322:
days_between_dates 2020-01-01 2020-09-06
249
</pre>
=={{header|S-BASIC}}==
Error checking of entered dates is omitted in order to focus
on the stated task but would obviously have to be included
in production code.
<syntaxhighlight lang = "BASIC">
comment
Given a month, day, and year in the Gregorian calendar,
return a numeric date which is equal to the number of
days since the start of the Common era.
end
function serial_date(da, mo, yr = integer) = real
var n = real
n = 365 * yr + da + 31 * (mo - 1)
if mo >= 3 then
n = n - int(.4 * mo + 2.3)
else
yr = yr - 1
n = n + int(yr/4) - int(.75 * (int(yr/100) + 1))
end = n
comment
Read a date in YYYY-MM-DD format from the console and
return its serial date equivalent.
end
function get_date = real
var date = string : 20
var y, m, d = integer
input2 date
y = val(mid(date,1,4))
m = val(mid(date,6,2))
d = val(mid(date,9,2))
end = serial_date(d, m, y)
rem -- main program begins here
var date1, date2 = real
var another = char
repeat
begin
print "First date : ";
date1 = get_date
print "Second date : ";
date2 = get_date
print "Elapsed days = "; date2 - date1
input "Do another (y/n)"; another
end
until not another
end
</syntaxhighlight>
{{out}}
Test dates taken from Delphi example
<pre>
First date : 1970-01-01
Second date : 2019-10-18
Elapsed days = 18187
Do another (y/n)? n
</pre>
Line 2,282 ⟶ 2,595:
=={{header|Wren}}==
{{libheader|Wren-date}}
<syntaxhighlight lang="
var datePairs = [
Line 2,297 ⟶ 2,610:
["2020-02-29", "2020-03-01"]
]
Date.default = Date.isoDate
for (dates in datePairs) {
var date1 = Date.parse(dates[0])
var date2 = Date.parse(dates[1])
var days = (date2 - date1).days
System.print("Days between %(date1) and %(date2) = %(days)")
}</syntaxhighlight>
Line 2,318 ⟶ 2,631:
Days between 2019-03-29 and 2029-03-29 = 3653
Days between 2020-02-29 and 2020-03-01 = 1
</pre>
=={{header|XPL0}}==
{{trans|FreeBASIC}}
<syntaxhighlight lang "XPL0">func Gregorian(Y, M, D); \Return Gregorian day given date
int Y, M, D;
int N, W;
[N:= M + 9 - (M+9)/12*12;
W:= Y - N/10;
return 365*W + W/4 - W/100 + W/400 + (N*306+5)/10 + D - 1;
];
int Dates, N, Y, M, D, G0, G1;
[Dates:= [
["2019-01-01", "2019-01-02"],
["2019-01-02", "2019-01-01"],
["2019-01-01", "2019-03-01"],
["2020-01-01", "2020-03-01"],
["1995-11-21", "1995-11-21"],
["2090-01-01", "2098-12-25"] ];
OpenO(8); OpenI(8);
for N:= 0 to 6-1 do
[Text(8, Dates(N,0));
Y:= IntIn(8); M:= IntIn(8); D:= IntIn(8);
G0:= Gregorian(Y, M, D);
Text(8, Dates(N,1));
Y:= IntIn(8); M:= IntIn(8); D:= IntIn(8);
G1:= Gregorian(Y, M, D);
Text(0, "Number of days between "); Text(0, Dates(N,0)); Text(0, " and ");
Text(0, Dates(N,1)); Text(0, " is "); IntOut(0, abs(G1-G0)); CrLf(0);
];
]</syntaxhighlight>
{{out}}
<pre>
Number of days between 2019-01-01 and 2019-01-02 is 1
Number of days between 2019-01-02 and 2019-01-01 is 1
Number of days between 2019-01-01 and 2019-03-01 is 59
Number of days between 2020-01-01 and 2020-03-01 is 60
Number of days between 1995-11-21 and 1995-11-21 is 0
Number of days between 2090-01-01 and 2098-12-25 is 3280
</pre>
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