Last Friday of each month

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Task
Last Friday of each month
You are encouraged to solve this task according to the task description, using any language you may know.
Task

Write a program or a script that returns the last Fridays of each month of a given year.

The year may be given through any simple input method in your language (command line, std in, etc).


Example of an expected output:

./last_fridays 2012
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28


Related tasks



Ada[edit]

Uses GNAT. Applicable to any day of the week, cf. [[1]].

with Ada.Text_IO, GNAT.Calendar.Time_IO, Ada.Command_Line,
Ada.Calendar.Formatting, Ada.Calendar.Arithmetic;
 
procedure Last_Weekday_In_Month is
 
procedure Put_Line(T: Ada.Calendar.Time) is
use GNAT.Calendar.Time_IO;
begin
Ada.Text_IO.Put_Line(Image(Date => T, Picture => ISO_Date));
end Put_Line;
 
use Ada.Calendar, Ada.Calendar.Arithmetic;
subtype Day_Name is Formatting.Day_Name; use type Formatting.Day_Name;
 
T, Selected : Time;
Weekday: Day_Name  := Day_Name'Value(Ada.Command_Line.Argument (1));
Year : Year_Number := Integer'Value (Ada.Command_Line.Argument (2));
 
begin
for Month in 1 .. 12 loop
T := Time_Of (Year => Year, Month => Month, Day => 01);
while Ada.Calendar.Month(T) = Month loop
if Formatting.Day_Of_Week (T) = Weekday then
Selected := T;
end if;
T := T + Day_Count(1);
end loop;
Put_Line(Selected);
end loop;
end Last_Weekday_In_Month;
Output:
>./last_weekday_in_month friday 2012
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28


AppleScript[edit]

Translation of: JavaScript


on run argv
 
intercalate(linefeed, ¬
map(isoRow, ¬
transpose(map(lastFridaysOfYear, ¬
apply(cond(class of argv is list and argv ≠ {}, ¬
singleYearOrRange, fiveCurrentYears), argIntegers(argv))))))
 
end run
 
-- ARGUMENT HANDLING
 
-- Up to two optional command line arguments: [yearFrom], [yearTo]
-- (Default range in absence of arguments: from two years ago, to two years ahead)
 
-- ~ $ osascript ~/Desktop/lastFridays.scpt
-- ~ $ osascript ~/Desktop/lastFridays.scpt 2013
-- ~ $ osascript ~/Desktop/lastFridays.scpt 2013 2016
 
-- singleYearOrRange :: [Int] -> [Int]
on singleYearOrRange(argv)
apply(cond(length of argv > 0, my range, my fiveCurrentYears), argv)
end singleYearOrRange
 
-- fiveCurrentYears :: () -> [Int]
on fiveCurrentYears(_)
set intThisYear to year of (current date)
range({intThisYear - 2, intThisYear + 2})
end fiveCurrentYears
 
-- argIntegers :: maybe [String] -> [Int]
on argIntegers(argv)
if class of argv is list and argv ≠ {} then
{map(my parseInt, argv)}
else
{}
end if
end argIntegers
 
 
-- DERIVATION OF LAST FRIDAYS
 
-- lastFridaysOfYear :: Int -> [Date]
on lastFridaysOfYear(y)
lastWeekDaysOfYear(y, Friday as integer)
end lastFridaysOfYear
 
 
-- lastWeekDaysOfYear :: Int -> Int -> [Date]
on lastWeekDaysOfYear(intYear, iWeekday)
map(mclosure(my lastWeekDay, ¬
{intYear:intYear, iWeekday:iWeekday}), my lastDaysOfMonths(intYear))
end lastWeekDaysOfYear
 
 
-- lastWeekDay :: Int -> Int -> Date
on lastWeekDay(iLastDay, iMonth)
set iYear to intYear of my closure
 
calendarDate(iYear, iMonth, iLastDay - ¬
(((weekday of calendarDate(iYear, iMonth, iLastDay)) as integer) + ¬
(7 - (iWeekday of my closure))) mod 7)
end lastWeekDay
 
 
-- lastDaysOfMonths :: Int -> [Int]
on lastDaysOfMonths(y)
{31, cond(isLeapYear(y), 29, 28), 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
end lastDaysOfMonths
 
-- isLeapYear :: Int -> Bool
on isLeapYear(y)
(0 = y mod 4) and (0 ≠ y mod 100) or (0 = y mod 400)
end isLeapYear
 
 
 
 
-- GENERIC FUNCTIONS
 
-- Dates and date strings
 
-- calendarDate :: Int -> Int -> Int -> Date
on calendarDate(intYear, intMonth, intDay)
tell (current date)
set {its year, its month, its day, its time} to ¬
{intYear, intMonth, intDay, 0}
return it
end tell
end calendarDate
 
-- isoDateString :: Date -> String
on isoDateString(dte)
(((year of dte) as string) & ¬
"-" & text items -2 thru -1 of ¬
("0" & ((month of dte) as integer) as string)) & ¬
"-" & text items -2 thru -1 of ¬
("0" & day of dte)
end isoDateString
 
-- parseInt :: String -> Int
on parseInt(s)
s as integer
end parseInt
 
-- Testing and tabulation
 
-- transpose :: [[a]] -> [[a]]
on transpose(xss)
script mf
on lambdaCol(_, iCol)
map(mclosure(my closure's mf's lambdaRow, ¬
{iCol:iCol}), my closure's xss)
end lambdaCol
 
on lambdaRow(row)
item (my closure's iCol) of row
end lambdaRow
end script
map(mclosure(mf's lambdaCol, {xss:xss, mf:mf}), item 1 of xss)
end transpose
 
-- intercalate :: Text -> [Text] -> Text
on intercalate(strText, lstText)
set {dlm, my text item delimiters} to ¬
{my text item delimiters, strText}
set strJoined to lstText as text
set my text item delimiters to dlm
return strJoined
end intercalate
 
-- isoRow :: [Date] -> String
on isoRow(lstDate)
intercalate(tab, map(my isoDateString, lstDate))
end isoRow
 
-- range :: (Int, Int) -> [Int]
on range(tuple)
if tuple = {} then return {}
if length of tuple > 1 then
set {m, n} to tuple
else
return item 1 of tuple
end if
set lng to (n - m) + 1
set base to m - 1
set lst to {}
repeat with i from 1 to lng
set end of lst to i + base
end repeat
return lst
end range
 
-- Higher-order functions
 
-- map :: (a -> b) -> [a] -> [b]
on map(f, xs)
set mf to mReturn(f)
set lng to length of xs
set lst to {}
repeat with i from 1 to lng
set end of lst to lambda(item i of xs, i, xs) of mf
end repeat
return lst
end map
 
-- Lift 2nd class handler function into 1st class script wrapper
-- mReturn :: Handler -> Script
on mReturn(f)
if class of f is script then return f
script
property lambda : f
end script
end mReturn
 
-- Handler -> Record -> Script
on mclosure(f, recBindings)
script
property closure : recBindings
property lambda : f
end script
end mclosure
 
-- cond :: Bool -> (a -> b) -> (a -> b) -> (a -> b)
on cond(bool, f, g)
if bool then
f
else
g
end if
end cond
 
-- apply (a -> b) -> a -> b
on apply(f, a)
mReturn(f)'s lambda(a)
end apply
 
 


Output:
2014-01-31    2015-01-30    2016-01-29    2017-01-27    2018-01-26
2014-02-28    2015-02-27    2016-02-26    2017-02-24    2018-02-23
2014-03-28    2015-03-27    2016-03-25    2017-03-31    2018-03-30
2014-04-25    2015-04-24    2016-04-29    2017-04-28    2018-04-27
2014-05-30    2015-05-29    2016-05-27    2017-05-26    2018-05-25
2014-06-27    2015-06-26    2016-06-24    2017-06-30    2018-06-29
2014-07-25    2015-07-31    2016-07-29    2017-07-28    2018-07-27
2014-08-29    2015-08-28    2016-08-26    2017-08-25    2018-08-31
2014-09-26    2015-09-25    2016-09-30    2017-09-29    2018-09-28
2014-10-31    2015-10-30    2016-10-28    2017-10-27    2018-10-26
2014-11-28    2015-11-27    2016-11-25    2017-11-24    2018-11-30
2014-12-26    2015-12-25    2016-12-30    2017-12-29    2018-12-28

AutoHotkey[edit]

if 1 = ; no parameter passed
{
InputBox, 1, Last Fridays of year, Enter a year:, , , , , , , , %A_YYYY%
If ErrorLevel
ExitApp
}
 
YYYY = %1% ; retrieve command line parameter
Stmp = %YYYY%0101000000
count= 0
 
While count < 12
{
FormatTime, ddd, %stmp%, ddd
FormatTime, M, %stmp%, M
If (ddd = "Fri"){
if (M-1 = count){
t := stmp
stmp += 7, days
}
else
res .= SubStr(t, 1, 4) "-" SubStr(t, 5, 2) "-" SubStr(t, 7, 2) "`n"
,count++
,stmp := YYYY . SubStr("0" M, -1) . "01"
}
else
stmp += 1, days
}
MsgBox % res
Output:
for 2012:
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

AutoIt[edit]

 
#include <Date.au3>
 
$iYear = InputBox('Last Friday in each month', 'Please input the year:')
 
_GetLastFridays($iYear)
 
Func _GetLastFridays($_iYear)
Local $sResult = 'last fridays in ' & $_iYear & @LF, $iDay
Local $aDaysInMonth[12] = [31,28,31,30,31,30,31,31,30,31,30,31]
If _DateIsLeapYear($_iYear) Then $aDaysInMonth[1] = 29
For $i = 1 To 12
$iDay = $aDaysInMonth[$i-1]
While 1
If _DateToDayOfWeekISO($_iYear, $i, $iDay) = 5 Then
$sResult &= StringFormat('%4d-%02d-%02d', $_iYear, $i, $iDay) & @LF
ExitLoop
EndIf
$iDay -= 1
WEnd
Next
ConsoleWrite($sResult)
EndFunc ;==>_GetFridays
 
Output:
last fridays in 2012
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

--BugFix (talk) 13:27, 15 November 2013 (UTC)

AWK[edit]

 
# syntax: GAWK -f LAST_FRIDAY_OF_EACH_MONTH.AWK year
# converted from Fortran
BEGIN {
split("31,28,31,30,31,30,31,31,30,31,30,31",daynum_array,",") # days per month in non leap year
year = ARGV[1]
if (year % 400 == 0 || (year % 4 == 0 && year % 100 != 0)) {
daynum_array[2] = 29
}
y = year - 1
k = 44 + y + int(y/4) + int(6*(y/100)) + int(y/400)
for (m=1; m<=12; m++) {
k += daynum_array[m]
d = daynum_array[m] - (k%7)
printf("%04d-%02d-%02d\n",year,m,d)
}
exit(0)
}
 
Output:
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

Befunge[edit]

Translation of: C

The algorithm has been slightly simplified to avoid the additional day adjustment inside the loop, and the year is obtained from stdin rather than via the command line.

":raeY",,,,,&>55+,:::45*:*%\"d"%!*\4%+!3v
v2++1**"I"5\+/*:*54\-/"d"\/4::-1::p53+g5<
>:00p5g4-+7%\:0\v>,"-",5g+:55+/68*+,55+%v
^<<_$$vv*86%+55:<^+*86%+55,+*86/+55:-1:<6
>$$^@$<>+\55+/:#^_$>:#,_$"-",\:04-\-00g^8
^<# #"#"##"#"##!` +76:+1g00,+55,+*<
Output:
Year:2012

2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

C[edit]

Doesn't work with Julian calendar (then again, you probably don't need to plan your weekends for middle ages).

#include <stdio.h>
#include <stdlib.h>
 
int main(int c, char *v[])
{
int days[] = {31,29,31,30,31,30,31,31,30,31,30,31};
int m, y, w;
 
if (c < 2 || (y = atoi(v[1])) <= 1700) return 1;
days[1] -= (y % 4) || (!(y % 100) && (y % 400));
w = y * 365 + (y - 1) / 4 - (y - 1) / 100 + (y - 1) / 400 + 6;
 
for(m = 0; m < 12; m++) {
w = (w + days[m]) % 7;
printf("%d-%02d-%d\n", y, m + 1,
days[m] + (w < 5 ? -2 : 5) - w);
}
 
return 0;
}

C#[edit]

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
 
namespace RosettaCode.LastFridaysOfYear
{
internal static class Program
{
private static IEnumerable<DateTime> LastFridaysOfYear(int year)
{
for (var month = 1; month <= 12; month++)
{
var date = new DateTime(year, month, 1).AddMonths(1).AddDays(-1);
while (date.DayOfWeek != DayOfWeek.Friday)
{
date = date.AddDays(-1);
}
yield return date;
}
}
 
private static void Main(string[] arguments)
{
int year;
var argument = arguments.FirstOrDefault();
if (string.IsNullOrEmpty(argument) || !int.TryParse(argument, out year))
{
year = DateTime.Today.Year;
}
 
foreach (var date in LastFridaysOfYear(year))
{
Console.WriteLine(date.ToString("d", CultureInfo.InvariantCulture));
}
}
}
}
Output:
01/27/2012
02/24/2012
03/30/2012
04/27/2012
05/25/2012
06/29/2012
07/27/2012
08/31/2012
09/28/2012
10/26/2012
11/30/2012
12/28/2012

C++[edit]

Library: Boost

called with ./last_fridays 2012

#include <boost/date_time/gregorian/gregorian.hpp>
#include <iostream>
#include <cstdlib>
 
int main( int argc , char* argv[ ] ) {
using namespace boost::gregorian ;
 
greg_month months[ ] = { Jan , Feb , Mar , Apr , May , Jun , Jul ,
Aug , Sep , Oct , Nov , Dec } ;
greg_year gy = atoi( argv[ 1 ] ) ;
for ( int i = 0 ; i < 12 ; i++ ) {
last_day_of_the_week_in_month lwdm ( Friday , months[ i ] ) ;
date d = lwdm.get_date( gy ) ;
std::cout << d << std::endl ;
}
return 0 ;
}
Output:
2012-Jan-27
2012-Feb-24
2012-Mar-30
2012-Apr-27
2012-May-25
2012-Jun-29
2012-Jul-27
2012-Aug-31
2012-Sep-28
2012-Oct-26
2012-Nov-30
2012-Dec-28

Clojure[edit]

Library: clj-time
(use '[clj-time.core :only [last-day-of-the-month day-of-week minus days]]
'[clj-time.format :only [unparse formatters]])
 
(defn last-fridays [year]
(let [last-days (map #(last-day-of-the-month year %) (range 1 13 1))
dow (map day-of-week last-days)
relation (zipmap last-days dow)]
(map #(minus (key %) (days (mod (+ (val %) 2) 7))) relation)))
 
(defn last-fridays-formatted [year]
(sort (map #(unparse (formatters :year-month-day) %) (last-fridays year))))
Output:
user=> (pprint (last-fridays-formatted 2012))
("2012-01-27"
 "2012-02-24"
 "2012-03-30"
 "2012-04-27"
 "2012-05-25"
 "2012-06-29"
 "2012-07-27"
 "2012-08-31"
 "2012-09-28"
 "2012-10-26"
 "2012-11-30"
 "2012-12-28")

COBOL[edit]

 
program-id. last-fri.
data division.
working-storage section.
1 wk-date.
2 yr pic 9999.
2 mo pic 99 value 1.
2 da pic 99 value 1.
1 rd-date redefines wk-date pic 9(8).
1 binary.
2 int-date pic 9(8).
2 dow pic 9(4).
2 friday pic 9(4) value 5.
procedure division.
display "Enter a calendar year (1601 thru 9999): "
with no advancing
accept yr
if yr >= 1601 and <= 9999
continue
else
display "Invalid year"
stop run
end-if
perform 12 times
move 1 to da
add 1 to mo
if mo > 12 *> to avoid y10k in 9999
move 12 to mo
move 31 to da
end-if
compute int-date = function
integer-of-date (rd-date)
if mo =12 and da = 31 *> to avoid y10k in 9999
continue
else
subtract 1 from int-date
end-if
compute rd-date = function
date-of-integer (int-date)
compute dow = function mod
((int-date - 1) 7) + 1
compute dow = function mod ((dow - friday) 7)
subtract dow from da
display yr "-" mo "-" da
add 1 to mo
end-perform
stop run
.
end program last-fri.
 
Output:
2016-01-29
2016-02-26
2016-03-25
2016-04-29
2016-05-27
2016-06-24
2016-07-29
2016-08-26
2016-09-30
2016-10-28
2016-11-25
2016-12-30

CoffeeScript[edit]

 
last_friday_of_month = (year, month) ->
# month is 1-based, JS API is 0-based, then we use
# non-positive indexes to work backward relative to the
# first day of the next month
i = 0
while true
last_day = new Date(year, month, i)
if last_day.getDay() == 5
return last_day.toDateString()
i -= 1
 
print_last_fridays_of_month = (year) ->
for month in [1..12]
console.log last_friday_of_month year, month
 
do ->
year = parseInt process.argv[2]
print_last_fridays_of_month year
 
Output:
 
> coffee last_friday.coffee 2012
Fri Jan 27 2012
Fri Feb 24 2012
Fri Mar 30 2012
Fri Apr 27 2012
Fri May 25 2012
Fri Jun 29 2012
Fri Jul 27 2012
Fri Aug 31 2012
Fri Sep 28 2012
Fri Oct 26 2012
Fri Nov 30 2012
Fri Dec 28 2012
 

Common Lisp[edit]

Works with: CLISP

The command-line argument processing is the only CLISP-specific code.

(defun friday-before (year month day)
(let*
((timestamp (encode-universal-time 0 0 12 day month year))
(weekday (nth 6 (multiple-value-list (decode-universal-time timestamp))))
(fri (- timestamp (* (+ (mod (+ weekday 2) 7) 1) 86400))))
(multiple-value-bind (_ _ _ d m y) (decode-universal-time fri)
(list y m d))))
 
(defun last-fridays (year)
(append (loop for month from 2 to 12 collecting (friday-before year month 1))
(list (friday-before (1+ year) 1 1))))
 
(let* ((year (read-from-string (car *args*))))
(format t "~{~{~a-~2,'0d-~2,'0d~}~%~}" (last-fridays year)))

Sample run for the year 2015:

Output:
2015-01-30
2015-02-27
2015-03-27
2015-04-24
2015-05-29
2015-06-26
2015-07-31
2015-08-28
2015-09-25
2015-10-30
2015-11-27
2015-12-25

D[edit]

import std.stdio, std.datetime, std.traits;
 
void lastFridays(in uint year) {
auto date = Date(year, 1, 1);
foreach (_; [EnumMembers!Month]) {
date.day(date.daysInMonth);
date.roll!"days"(-(date.dayOfWeek + 2) % 7);
writeln(date);
date.add!"months"(1, AllowDayOverflow.no);
}
}
 
void main() {
lastFridays(2012);
}
2012-Jan-27
2012-Feb-24
2012-Mar-30
2012-Apr-27
2012-May-25
2012-Jun-29
2012-Jul-27
2012-Aug-31
2012-Sep-28
2012-Oct-26
2012-Nov-30
2012-Dec-28

Elixir[edit]

defmodule RC do
def lastFriday(year) do
Enum.map(1..12, fn month ->
lastday = :calendar.last_day_of_the_month(year, month)
daynum = :calendar.day_of_the_week(year, month, lastday)
friday = lastday - rem(daynum + 2, 7)
{year, month, friday}
end)
end
end
 
y = String.to_integer(hd(System.argv))
Enum.each(RC.lastFriday(y), fn {year, month, day} ->
 :io.format "~4b-~2..0w-~2..0w~n", [year, month, day]
end)
Output:
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

Elm[edit]

import Html exposing (Html, Attribute, text, div, input)
import Html.App exposing (beginnerProgram)
import Html.Attributes exposing (placeholder, value, style)
import Html.Events exposing (onInput)
import String exposing (toInt)
import Maybe exposing (withDefault)
import List exposing (map, map2)
import List.Extra exposing (scanl1)
 
type Msg = SetYear String
 
lastFridays : Int -> List Int
lastFridays year =
let isLeap = (year % 400) == 0 || ( (year % 4) == 0 && (year % 100) /= 0 )
daysInMonth = [31, if isLeap then 29 else 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
y = year-1
in scanl1 (+) daysInMonth
|> map2 (\len day -> len - (day + 2 + y + y//4 - y//100 + y//400) % 7) daysInMonth
 
lastFridayStrings : String -> List String
lastFridayStrings yearString =
let months= ["January ", "February ", "March ", "April ", "May ", "June ", "July ", "August ", "September ", "October ", "November ", "December "]
errString = "Only years after 1752 are valid."
in case toInt yearString of
Ok year ->
if (year < 1753)
then [errString]
else lastFridays year
|> map2 (\m d -> m ++ toString d ++ ", " ++ toString year) months
Err _ ->
[errString]
 
view : String -> Html Msg
view yearString =
div []
([ input
[ placeholder "Enter a year."
, value yearString
, onInput SetYear
, myStyle
]
[]
] ++ (lastFridayStrings yearString
|> map (\date -> div [ myStyle ] [ text date ]) ))
 
myStyle : Attribute Msg
myStyle =
style
[ ("width", "100%")
, ("height", "20px")
, ("padding", "5px 0 0 5px")
, ("font-size", "1em")
, ("text-align", "left")
]
 
update : Msg -> String -> String
update msg _ =
case msg of
SetYear yearString -> yearString
 
 
main =
beginnerProgram
{ model = ""
, view = view
, update = update
}

Link to live demo: http://dc25.github.io/lastFridayOfMonthElm/

Sample run for the year 2003; copied and pasted from web-page:

Output:
January 31, 2003
February 28, 2003
March 28, 2003
April 25, 2003
May 30, 2003
June 27, 2003
July 25, 2003
August 29, 2003
September 26, 2003
October 31, 2003
November 28, 2003
December 26, 2003

Erlang[edit]

 
-module( last_date_each_month ).
 
-export( [monday/1, tuesday/1, wednesday/1, thursday/1, friday/1, saturday/1, sunday/1] ).
 
monday( Year ) -> last( Year, 1 ).
tuesday( Year ) -> last( Year, 2 ).
wednesday( Year ) -> last( Year, 3 ).
thursday( Year ) -> last( Year, 4 ).
friday( Year ) -> last( Year, 5 ).
saturday( Year ) -> last( Year, 6 ).
sunday( Year ) -> last( Year, 7 ).
 
 
 
last( Year, Week_day ) ->
Months = lists:seq( 1, 12 ),
Months_days = [{X, Y} || X <- Months, Y <- lists:seq(calendar:last_day_of_the_month(Year, X), calendar:last_day_of_the_month(Year, X) - 7, -1), calendar:valid_date(Year, X, Y), calendar:day_of_the_week(Year, X, Y) =:= Week_day],
[{Year, X, proplists:get_value(X, Months_days)} || X <- Months].
 
Output:
32> [io:fwrite("~B-~2.10.0B-~B~n", [Y,M,D]) || {Y,M,D} <- last_date_each_month:friday(2012)].
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

Fortran[edit]

Algorithm: compute day of week for last day of month, then subtract just enough to get to the preceding friday. Do this for each month. To simplify computations further, we only need to compute day of week of january 1st (the others are found by adding month lengths). Since day of week need only be known modulo 7, we do not compute modulo at all except once when subtracting.

program fridays
implicit none
integer :: days(1:12) = (/31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31/)
integer :: year, k, y, m
read *, year
if (mod(year, 400) == 0 .or. (mod(year, 4) == 0 .and. mod(year, 100) /= 0)) days(2) = 29
y = year - 1
k = 44 + y + y/4 + 6*(y/100) + y/400
do m = 1, 12
k = k + days(m)
print "(I4,A1,I2.2,A1,I2)", year, '-', m, '-', days(m) - mod(k, 7)
end do
end program
 

FreeBASIC[edit]

' version 23-06-2015
' compile with: fbc -s console
 
#Ifndef TRUE ' define true and false for older freebasic versions
#Define FALSE 0
#Define TRUE Not FALSE
#EndIf
 
Function leapyear(Year_ As Integer) As Integer
' from the leapyeat entry
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
 
Function wd(m As Integer, d As Integer, y As Integer) As Integer
' Zellerish
' 0 = Sunday, 1 = Monday, 2 = Tuesday, 3 = Wednesday
' 4 = Thursday, 5 = Friday, 6 = Saturday
 
If m < 3 Then ' If m = 1 Or m = 2 Then
m += 12
y -= 1
End If
Return (y + (y \ 4) - (y \ 100) + (y \ 400) + d + ((153 * m + 8) \ 5)) Mod 7
End Function
 
' ------=< MAIN >=------
 
Type month_days
m_name As String
days As UByte
End Type
 
Dim As month_days arr(1 To 12)
Data "January", 31, "February", 28, "March", 31, "April", 30
Data "May", 31, "June", 30, "July", 31, "August", 31
Data "September", 30, "October", 31, "November", 30, "December", 31
 
Dim As Integer yr, d, i, x
Dim As String keypress
 
For i = 1 To 12
With arr(i)
Read .m_name
Read .days
End With
Next
 
Do
 
Do
Print "For what year do you want to find the last Friday of the month"
Input "any number below 1800 stops program, year in YYYY format";yr
' empty input also stops
If yr < 1800 Then
End
Else
Exit Do
End If
Loop
 
Print : Print
Print "Last Friday of the month for"; yr
 
For i = 1 To 12
d = arr(i).days
If i = 2 AndAlso leapyear(yr) = TRUE Then d = d + 1
x = wd(i, d, yr)
If x <> 5 Then d = d - IIf(x > 5, x - 5, x + 2)
Print d; " "; arr(i).m_name
Next
 
' empty key buffer
While InKey <> "" : keypress = InKey : Wend
Print : Print
Print "Find last Friday for a other year [Y|y], anything else stops"
keypress =""
While keypress = "" : keypress = InKey : Wend
If LCase(keypress) <> "y" Then Exit Do
Print : Print
 
Loop
End
Output:
For what year do you want to find the last Friday of the month
any number below 1800 stops program, year in YYYY format? 2015

Last Friday of the month for 2015
 30 January
 27 February
 27 March
 24 April
 29 May
 26 June
 31 July
 28 August
 25 September
 30 October
 27 November
 25 December

Go[edit]

package main
 
import (
"fmt"
"os"
"strconv"
"time"
)
 
func main() {
y := time.Now().Year()
if len(os.Args) == 2 {
if i, err := strconv.Atoi(os.Args[1]); err == nil {
y = i
}
}
for m := time.January; m <= time.December; m++ {
d := time.Date(y, m+1, 1, 0, 0, 0, 0, time.UTC).Add(-24 * time.Hour)
d = d.Add(-time.Duration((d.Weekday()+7-time.Friday)%7) * 24 * time.Hour)
fmt.Println(d.Format("2006-01-02"))
}
}
Output:
> ./fridays 2012
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

Groovy[edit]

Solution: Same as Find last Sunday of each month

Test:

def ymd = { it.format('yyyy-MM-dd') }
def lastFridays = lastWeekDays.curry(Day.Fri)
lastFridays(args[0] as int).each { println (ymd(it)) }

Execution (Cygwin on Windows 7):

[2273] groovy lastFridays.groovy 2012
Output:
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

Haskell[edit]

import Data.Time.Calendar
import Data.Time.Calendar.WeekDate
 
findFriday date = head $ filter isFriday $ map toDate [-6 .. 0]
where
toDate ago = addDays ago date
isFriday theDate = let (_ , _ , day) = toWeekDate theDate
in day == 5
 
fridayDates year = map (showGregorian . findFriday) lastDaysInMonth
where
lastDaysInMonth = map findLastDay [1 .. 12]
findLastDay month = fromGregorian year month (gregorianMonthLength year month)
 
main = do
putStrLn "Please enter a year!"
year <- getLine
mapM_ putStrLn $ fridayDates (read year)
Output:
Please enter a year!
2012
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

Icon and Unicon[edit]

This will write the last fridays for every year given as an argument. There is no error checking on the year.

procedure main(A)
every write(lastfridays(!A))
end
 
procedure lastfridays(year)
every m := 1 to 12 do {
d := case m of {
2 : if IsLeapYear(year) then 29 else 28
4|6|9|11 : 30
default : 31
} # last day of month
 
z := 0
j := julian(m,d,year) + 1 # first day of next month
until (j-:=1)%7 = 4 do z -:=1 # backup to last friday=4
suspend sprintf("%d-%d-%d",year,m,d+z)
}
end
 
link datetime, printf

printf.icn provides formatting datetime.icn provides julian and IsLeapYear

Output:
last_fridays.exe 2012
2012-1-27
2012-2-24
2012-3-30
2012-4-27
2012-5-25
2012-6-29
2012-7-27
2012-8-31
2012-9-28
2012-10-26
2012-11-30
2012-12-28

J[edit]

require 'dates'
last_fridays=: 12 {. [: ({:/.~ }:"1)@(#~ 5 = weekday)@todate (i.366) + todayno@,&1 1

In other words, start from January 1 of the given year, and count forward for 366 days, keeping the Fridays. Then pick the last remaining day within each represented month (which will be a Friday because we only kept the Fridays). Then pick the first 12 (since on a non-leap year which ends on a Thursday we would get an extra Friday).

Example use:

   last_fridays 2012
2012 1 27
2012 2 24
2012 3 30
2012 4 27
2012 5 25
2012 6 29
2012 7 27
2012 8 31
2012 9 28
2012 10 26
2012 11 30
2012 12 28

Java[edit]

Works with: Java version 1.5+
import java.text.*;
import java.util.*;
 
public class LastFridays {
 
public static void main(String[] args) throws Exception {
int year = Integer.parseInt(args[0]);
GregorianCalendar c = new GregorianCalendar(year, 0, 1);
 
for (String mon : new DateFormatSymbols(Locale.US).getShortMonths()) {
if (!mon.isEmpty()) {
int totalDaysOfMonth = c.getActualMaximum(Calendar.DAY_OF_MONTH);
c.set(Calendar.DAY_OF_MONTH, totalDaysOfMonth);
 
int daysToRollBack = (c.get(Calendar.DAY_OF_WEEK) + 1) % 7;
 
int day = totalDaysOfMonth - daysToRollBack;
c.set(Calendar.DAY_OF_MONTH, day);
 
System.out.printf("%d %s %d\n", year, mon, day);
 
c.set(year, c.get(Calendar.MONTH) + 1, 1);
}
}
}
}
Output:
(for java LastFridays 2012):
2012 Jan 27
2012 Feb 24
2012 Mar 30
2012 Apr 27
2012 May 25
2012 Jun 29
2012 Jul 27
2012 Aug 31
2012 Sep 28
2012 Oct 26
2012 Nov 30
2012 Dec 28


JavaScript[edit]

Imperative[edit]

Works with: Nodejs
 
var last_friday_of_month, print_last_fridays_of_month;
 
last_friday_of_month = function(year, month) {
var i, last_day;
i = 0;
while (true) {
last_day = new Date(year, month, i);
if (last_day.getDay() === 5) {
return last_day.toDateString();
}
i -= 1;
}
};
 
print_last_fridays_of_month = function(year) {
var month, results;
results = [];
for (month = 1; month <= 12; ++month) {
results.push(console.log(last_friday_of_month(year, month)));
}
return results;
};
 
(function() {
var year;
year = parseInt(process.argv[2]);
return print_last_fridays_of_month(year);
})();
 
 
Output:
 
>node lastfriday.js 2015
Fri Jan 30 2015
Fri Feb 27 2015
Fri Mar 27 2015
Fri Apr 24 2015
Fri May 29 2015
Fri Jun 26 2015
Fri Jul 31 2015
Fri Aug 28 2015
Fri Sep 25 2015
Fri Oct 30 2015
Fri Nov 27 2015
Fri Dec 25 2015
 


Functional (ES 5)[edit]

(function () {
'use strict';
 
// lastFridaysOfYear :: Int -> [Date]
function lastFridaysOfYear(y) {
return lastWeekDaysOfYear(y, days.friday);
}
 
// lastWeekDaysOfYear :: Int -> Int -> [Date]
function lastWeekDaysOfYear(y, iWeekDay) {
return [
31,
0 === y % 4 && 0 !== y % 100 || 0 === y % 400 ? 29 : 28,
31, 30, 31, 30, 31, 31, 30, 31, 30, 31
]
.map(function (d, m) {
var dte = new Date(Date.UTC(y, m, d));
 
return new Date(Date.UTC(
y, m, d - (
(dte.getDay() + (7 - iWeekDay)) % 7
)
));
});
}
 
 
 
 
// isoDateString :: Date -> String
function isoDateString(dte) {
return dte.toISOString()
.substr(0, 10);
}
 
// range :: Int -> Int -> [Int]
function range(m, n) {
return Array.apply(null, Array(n - m + 1))
.map(function (x, i) {
return m + i;
});
}
 
// transpose :: [[a]] -> [[a]]
function transpose(lst) {
return lst[0].map(function (_, iCol) {
return lst.map(function (row) {
return row[iCol];
});
});
}
 
var days = {
sunday: 0,
monday: 1,
tuesday: 2,
wednesday: 3,
thursday: 4,
friday: 5,
saturday: 6
}
 
// TEST
 
return transpose(
range(2012, 2016)
.map(lastFridaysOfYear)
)
.map(function (row) {
return row
.map(isoDateString)
.join('\t');
})
.join('\n');
 
})();
Output:
2012-01-27	2013-01-25	2014-01-31	2015-01-30	2016-01-29
2012-02-24	2013-02-22	2014-02-28	2015-02-27	2016-02-26
2012-03-30	2013-03-29	2014-03-28	2015-03-27	2016-03-25
2012-04-27	2013-04-26	2014-04-25	2015-04-24	2016-04-29
2012-05-25	2013-05-31	2014-05-30	2015-05-29	2016-05-27
2012-06-29	2013-06-28	2014-06-27	2015-06-26	2016-06-24
2012-07-27	2013-07-26	2014-07-25	2015-07-31	2016-07-29
2012-08-31	2013-08-30	2014-08-29	2015-08-28	2016-08-26
2012-09-28	2013-09-27	2014-09-26	2015-09-25	2016-09-30
2012-10-26	2013-10-25	2014-10-31	2015-10-30	2016-10-28
2012-11-30	2013-11-29	2014-11-28	2015-11-27	2016-11-25
2012-12-28	2013-12-27	2014-12-26	2015-12-25	2016-12-30

jq[edit]

Works with: jq version 1.4

Foundations

# In case your jq does not have "until" defined:
 
def until(cond; next):
def _until:
if cond then . else (next|_until) end;
_until;
 
# Zeller's Congruence is from [[Day_of_the_week#jq]]
 
# Use Zeller's Congruence to determine the day of the week, given
# year, month and day as integers in the conventional way.
# If iso == "iso" or "ISO", then emit an integer in 1 -- 7 where
# 1 represents Monday, 2 Tuesday, etc;
# otherwise emit 0 for Saturday, 1 for Sunday, etc.
#
def day_of_week(year; month; day; iso):
if month == 1 or month == 2 then
[year - 1, month + 12, day]
else
[year, month, day]
end
| .[2] + (13*(.[1] + 1)/5|floor)
+ (.[0]%100) + ((.[0]%100)/4|floor)
+ (.[0]/400|floor) - 2*(.[0]/100|floor)
| if iso == "iso" or iso == "ISO" then 1 + ((. + 5) % 7)
else . % 7
end ;

findLastFridays

# year and month are numbered conventionally 
def findLastFriday(year; month):
def isLeapYear:
year%4 == 0 and ( year%100!=0 or year%400==0 ) ;
def days:
if month == 2 then (if isLeapYear then 29 else 28 end)
else [31, 28, 31,30,31,30,31,31,30,31,30,31][month-1]
end;
year as $year
| month as $month
| days
| until( day_of_week($year; $month; .; null) == 6 ; .-1);
 
# input: year
def findLastFridays:
def months:
["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"];
. as $year
| "YEAR: \(.)",
(range(0;12) | "\(months[.]) \(findLastFriday($year; .+1))") ;
 
$year|tonumber|findLastFridays
Output:
$ jq --arg year 2012 -n -r -f findLastFridays.jq
YEAR: 2012
January 27
February 24
March 30
April 27
May 25
June 29
July 27
August 31
September 28
October 26
November 30
December 28

Julia[edit]

 
isdefined(:Date) || using Dates
 
const wday = Dates.Fri
const lo = 1
const hi = 12
 
print("\nThis script will print the last ", Dates.dayname(wday))
println("s of each month of the year given.")
println("(Leave input empty to quit.)")
 
while true
print("\nYear> ")
y = chomp(readline())
0 < length(y) || break
y = try
parseint(y)
catch
println("Sorry, but \"", y, "\" does not compute as a year.")
continue
end
println()
for m in Date(y, lo):Month(1):Date(y, hi)
println(" ", tolast(m, wday))
end
end
 

This code uses the Dates module, which is being incorporated into Julian's standard library with the current development version (0.4). I've used isdefined to make this code good for the current stable version (0.3) as well as for future releases. If Dates is not installed on your instance of Julian try Pkg.add("Dates") from the REPL.

Output:
This script will print the last Fridays of each month of the year given.
(Leave input empty to quit.)

Year> 2012

    2012-01-27
    2012-02-24
    2012-03-30
    2012-04-27
    2012-05-25
    2012-06-29
    2012-07-27
    2012-08-31
    2012-09-28
    2012-10-26
    2012-11-30
    2012-12-28

Year> this year 
Sorry, but "this year" does not compute as a year.

Year> 

Lasso[edit]

define isLeapYear(y::integer) => {
#y % 400 == 0 ? return true
#y % 100 == 0 ? return false
#y % 4 == 0 ? return true
return false
}
define fridays(y::integer) => {
local(out = array)
loop(12) => {
local(last = 28)
loop_count == 2 && isLeapYear(#y) ? #last = 29
array(4,6,9,11) >> loop_count ? #last == 30
#last == 28 && loop_count != 2 ? #last = 31
local(start = date(-year=#y,-month=loop_count,-day=#last))
while(#start->dayofweek != 6) => {
#start->subtract(-day=1)
}
#out->insert(#start)
}
return #out
}
with f in fridays(2012) do => {^
#f->format('%Q') + '\r'
^}
Output:
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28


LiveCode[edit]

function lastFriday yyyy
-- year,month num,day of month,hour in 24-hour time,minute,second,numeric day of week.
convert the long date to dateitems
put 1 into item 2 of it
put 1 into item 3 of it
put yyyy into item 1 of it
put it into startDate
convert startDate to dateItems
repeat with m = 1 to 12
put m into item 2 of startDate
repeat with d = 20 to 31
put d into item 3 of startDate
convert startDate to dateItems
-- 6 is friday
if item 7 of startDate is 6 and item 1 of startDate is yyyy and item 2 of startDate is m then
put item 3 of startDate into fridays[item 2 of startDate]
end if
end repeat
end repeat
combine fridays using cr and space
sort fridays ascending numeric
return fridays
end lastFriday
Example
put lastFriday("2012")
Output
1 27
2 24
3 30
4 27
5 25
6 29
7 27
8 31
9 28
10 26
11 30
12 28

[edit]

; Determine if a Gregorian calendar year is leap 
to leap? :year
output (and
equal? 0 modulo :year 4
not member? modulo :year 400 [100 200 300]
)
end
 
; Convert Gregorian calendar date to a simple day count from
; RD 1 = January 1, 1 CE
to day_number :year :month :day
local "elapsed make "elapsed difference :year 1
output (sum product 365 :elapsed
int quotient :elapsed 4
minus int quotient :elapsed 100
int quotient :elapsed 400
int quotient difference product 367 :month 362 12
ifelse lessequal? :month 2 0 ifelse leap? :year -1 -2
 :day)
end
 
; Find the day of the week from a day number, 0 = Sunday through 6 = Saturday
to day_of_week :day_number
output modulo :day_number 7
end
 
; Find the date of the last Friday of a given month
to last_friday :year :month
local "zero make "zero day_number :year :month 0
local "last make "last day_number :year sum 1 :month 0
local "wday make "wday day_of_week :last
local "friday make "friday sum :last remainder difference -2 :wday 7
output difference :friday :zero
end
 
local "year
make "year ifelse empty? :command.line 2012 :command.line
 
repeat 12 [
local "month make "month #
local "day make "day last_friday :year :month
if (less? :month 10) [make "month word "0 :month]
print reduce [(word ?1 "- ?2)] (list :year :month :day)
]
bye
Output:
$  logo last_fridays.lg - 2012
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

Lua[edit]

function isLeapYear (y)
return (y % 4 == 0 and y % 100 ~=0) or y % 400 == 0
end
 
function dayOfWeek (y, m, d)
local t = os.time({year = y, month = m, day = d})
return os.date("%A", t)
end
 
function lastWeekdays (wday, year)
local monthLength, day = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
if isLeapYear(year) then monthLength[2] = 29 end
for month = 1, 12 do
day = monthLength[month]
while dayOfWeek(year, month, day) ~= wday do day = day - 1 end
print(year .. "-" .. month .. "-" .. day)
end
end
 
lastWeekdays("Friday", tonumber(arg[1]))

Command line session:

>lua lastFridays.lua 2012
2012-1-27
2012-2-24
2012-3-30
2012-4-27
2012-5-25
2012-6-29
2012-7-27
2012-8-31
2012-9-28
2012-10-26
2012-11-30
2012-12-28

>

Mathematica[edit]

FridaysOfYear[Y_] := 
NestWhile[(DaysPlus[#, - 1]) &, #, (DateString[#, "DayName"] != "Friday") &] & /@
[email protected]@NestList [DaysPlus[# /. {x_, y_, X_} -> {x, y, 1}, - 1] &, {Y + 1, 1, 1}, 12]
[email protected][2012]
Output:
{2012,1,27}
{2012,2,24}
{2012,3,30}
{2012,4,27}
{2012,5,25}
{2012,6,29}
{2012,7,27}
{2012,8,31}
{2012,9,28}
{2012,10,26}
{2012,11,30}
{2012,12,28}

MATLAB / Octave[edit]

 function t = last_fridays_of_year(y)
t1 = datenum([y,1,1,0,0,0]);
t2 = datenum([y,12,31,0,0,0]);
t = datevec(t1:t2);
t = t(strmatch('Friday', datestr(t,'dddd')), :); % find all Fridays
t = t([find(diff(t(:,2)) > 0); end], :); % find Fridays before change of month
end;
 
datestr(last_fridays_of_year(2012),'yyyy-mm-dd')
 
Output:
  ans =
  2012-01-27
  2012-02-24
  2012-03-30
  2012-04-27
  2012-05-25
  2012-06-29
  2012-07-27
  2012-08-31
  2012-09-28
  2012-10-26
  2012-11-30
  2012-12-28

Maxima[edit]

weekday(year,  month,  day) := block([m: month,  y: year,  k], 
if m < 3 then (m: m + 12, y: y - 1),
k: 1 + remainder(day + quotient((m + 1)*26, 10) + y + quotient(y, 4)
+ 6*quotient(y, 100) + quotient(y, 400) + 5, 7),
['monday, 'tuesday, 'wednesday, 'thurdsday, 'friday, 'saturday, 'sunday][k]
)$
 
leapyearp(year) := is(mod(year, 4) = 0 and (mod(year, 100) # 0 or mod(year, 400) = 0))$
 
 
lastfridays(year) := block(
[m: [31, if leapyearp(year) then 29 else 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31], v: [ ]],
for month thru 12 do v: endcons(sconcat(year, "-", month, "-",
lmax(sublist(makelist(i, i, 1, m[month]), lambda([day], weekday(year, month, day) = 'friday)))), v),
v
)$
 
lastfridays(2012);
["2012-1-27", "2012-2-24", "2012-3-30", "2012-4-27", "2012-5-25", "2012-6-29",
"2012-7-27","2012-8-31", "2012-9-28", "2012-10-26", "2012-11-30", "2012-12-28"]

NetRexx[edit]

Translation of: Java
Translation of: C

Implements the algorithms from both the Java and C implementations.

/* NetRexx */
options replace format comments java crossref symbols nobinary
 
import java.text.
 
runSample(arg)
return
 
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
method lastFridayByLib(year) public static
 
cal = GregorianCalendar(year, 0, 1)
 
loop mon over DateFormatSymbols().getShortMonths()
if \mon.isEmpty() then do
totalDaysOfMonth = cal.getActualMaximum(Calendar.DAY_OF_MONTH)
cal.set(Calendar.DAY_OF_MONTH, totalDaysOfMonth)
 
daysToRollBack = (cal.get(Calendar.DAY_OF_WEEK) + 1) // 7
 
day = totalDaysOfMonth - daysToRollBack
cal.set(Calendar.DAY_OF_MONTH, day)
 
say year.right(4, 0) mon day.right(2, 0)
 
cal.set(year, cal.get(Calendar.MONTH) + 1, 1)
end
end mon
return
 
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
method lastFridayCalc(year) public static binary signals BadArgumentException
 
if year <= 1700 then do
signal BadArgumentException(year 'is out of range')
end
 
wk = int
mth = int
yr = int year
days = [int 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31] -- days in month
days[1] = days[1] - ((yr // 4) | \(yr // 100) & (yr // 400)) -- adjust for leap year
 
wk = yr * 365 + (yr - 1) % 4 - (yr - 1) % 100 + (yr - 1) % 400 + 6 -- week number
 
loop mth = 0 to 11
wk = (wk + days[mth]) // 7
wx = int
if wk < 5 then wx = -2
else wx = 5
yy = Rexx(yr)
mm = Rexx(mth + 1)
dd = Rexx(days[mth] + wx - wk)
say yy.right(4, 0)'-'mm.right(2, 0)'-'dd.right(2, 0)
end mth
return
 
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
method runSample(arg) private static
do
parse arg year .
if year = '' | year = '.' then year = 2012
dlm = '-'
dlm = dlm.left(60, dlm)
say
say 'Using Java calendar libraries'
say dlm
lastFridayByLib(year)
say
say 'Calculated'
say dlm
lastFridayCalc(year)
catch ex = Exception
ex.printStackTrace
end
return
 
Output:
Using Java calendar libraries
------------------------------------------------------------
2012 Jan 27
2012 Feb 24
2012 Mar 30
2012 Apr 27
2012 May 25
2012 Jun 29
2012 Jul 27
2012 Aug 31
2012 Sep 28
2012 Oct 26
2012 Nov 30
2012 Dec 28

Calculated
------------------------------------------------------------
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

Nim[edit]

import times, os, strutils
 
var timeinfo = getLocalTime getTime()
timeinfo.year = paramStr(1).parseInt
for month in mJan .. mDec:
timeinfo.month = month
for day in countdown(31, 1):
timeinfo.monthday = day
let t = getLocalTime(timeInfoToTime timeinfo)
if t.month == month and t.weekday == dFri:
echo t.format "yyyy-MM-dd"
break

Sample usage:

./lastfriday 2012
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

OCaml[edit]

Using the module Unix from the standard OCaml library:

#load "unix.cma"
open Unix
 
let usage() =
Printf.eprintf "%s <year>\n" Sys.argv.(0);
exit 1
 
let print_date t =
Printf.printf "%d-%02d-%02d\n" (t.tm_year + 1900) (t.tm_mon + 1) t.tm_mday
 
let is_date_ok tm t =
(tm.tm_year = t.tm_year &&
tm.tm_mon = t.tm_mon &&
tm.tm_mday = t.tm_mday)
 
let () =
let _year =
try int_of_string Sys.argv.(1)
with _ -> usage()
in
let year = _year - 1900 in
let fridays = Array.make 12 (Unix.gmtime 0.0) in
for month = 0 to 11 do
for day_of_month = 1 to 31 do
let tm = { (Unix.gmtime 0.0) with
tm_year = year;
tm_mon = month;
tm_mday = day_of_month;
} in
let _, t = Unix.mktime tm in
if is_date_ok tm t (* check for months that have less than 31 days *)
&& t.tm_wday = 5 (* is a friday *)
then fridays.(month) <- t
done;
done;
Array.iter print_date fridays
Output:
$ ocaml last_fridays.ml 2012
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

With a dedicated library[edit]

open CalendarLib
 
let usage() =
Printf.eprintf "%s <year>\n" Sys.argv.(0);
exit 1
 
let print_date (year, month, day) =
Printf.printf "%d-%02d-%02d\n" year month day
 
let () =
let year =
try int_of_string Sys.argv.(1)
with _ -> usage()
in
let fridays = ref [] in
for month = 1 to 12 do
let num_days = Date.days_in_month (Date.make_year_month year month) in
let rec aux day =
if Date.day_of_week (Date.make year month day) = Date.Fri
then fridays := (year, month, day) :: !fridays
else aux (pred day)
in
aux num_days
done;
List.iter print_date (List.rev !fridays)

Run this script with the command:

ocaml unix.cma str.cma -I +calendar calendarLib.cma last_fridays.ml 2012


Oforth[edit]

import: date
 
: lastFridays(y)
| m |
Date.JANUARY Date.DECEMBER for: m [
Date newDate(y, m, Date.DaysInMonth(y, m))
while(dup dayOfWeek Date.FRIDAY <>) [ addDays(-1) ]
println
] ;
Output:
2012-01-27 00:00:00,000
2012-02-24 00:00:00,000
2012-03-30 00:00:00,000
2012-04-27 00:00:00,000
2012-05-25 00:00:00,000
2012-06-29 00:00:00,000
2012-07-27 00:00:00,000
2012-08-31 00:00:00,000
2012-09-28 00:00:00,000
2012-10-26 00:00:00,000
2012-11-30 00:00:00,000
2012-12-28 00:00:00,000

PARI/GP[edit]

\\ Normalized Julian Day Number from date
njd(D) =
{
my (m = D[2], y = D[1]);
 
if (D[2] > 2, m++, y--; m += 13);
 
(1461 * y) \ 4 + (306001 * m) \ 10000 + D[3] - 694024 + 2 - y \ 100 + y \ 400
}
 
\\ Date from Normalized Julian Day Number
njdate(J) =
{
my (a = J + 2415019, b = (4 * a - 7468865) \ 146097, c, d, m, y);
 
a += 1 + b - b \ 4 + 1524;
b = (20 * a - 2442) \ 7305;
c = (1461 * b) \ 4;
d = ((a - c) * 10000) \ 306001;
m = d - 1 - 12 * (d > 13);
y = b - 4715 - (m > 2);
d = a - c - (306001 * d) \ 10000;
 
[y, m, d]
}
 
for (m=1, 12, a=njd([2012,m+1,0]); print(njdate(a-(a+1)%7)))
Output:
[2012, 1, 27]
[2012, 2, 24]
[2012, 3, 30]
[2012, 4, 27]
[2012, 5, 25]
[2012, 6, 29]
[2012, 7, 27]
[2012, 8, 31]
[2012, 9, 28]
[2012, 10, 26]
[2012, 11, 30]
[2012, 12, 28]

Perl[edit]

#!/usr/bin/perl -w
use strict ;
use DateTime ;
use feature qw( say ) ;
 
foreach my $month ( 1..12 ) {
my $dt = DateTime->last_day_of_month( year => $ARGV[ 0 ] , month => $month ) ;
while ( $dt->day_of_week != 5 ) {
$dt->subtract( days => 1 ) ;
}
say $dt->ymd ;
}
Output:
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

Perl 6[edit]

sub MAIN (Int $year = Date.today.year) {
my @fri;
for Date.new("$year-01-01") .. Date.new("$year-12-31") {
@fri[.month] = .Str if .day-of-week == 5;
}
.say for @fri[1..12];
}

Example:

$ ./lastfri 2038
2038-01-29
2038-02-26
2038-03-26
2038-04-30
2038-05-28
2038-06-25
2038-07-30
2038-08-27
2038-09-24
2038-10-29
2038-11-26
2038-12-31

A solution without a result array to store things in:

sub MAIN (Int $year = Date.today.year) {
say ~.value.reverse.first: *.day-of-week == 5
for classify *.month, Date.new("$year-01-01") .. Date.new("$year-12-31");
}

Here, classify sorts the dates into one bin per month (but preserves the order in each bin). We then take the list inside each bin (.value) and find the last (.reverse.first) date which is a Friday.

Another variation where the data flow can be read left to right using feed operators:

sub MAIN (Int $year = Date.today.year) {
.say for Date.new("$year-01-01") .. Date.new("$year-12-31") ==> classify *.month ==>
map *.value.reverse.first: *.day-of-week == 5
}

Phix[edit]

include timedate.e
 
constant FRIDAY=6
 
procedure showlast(integer dow, integer doy, timedate td)
td = adjust_timedate(td,timedelta(days:=doy-1))
integer {year,month,day} = td
while day_of_week(year,month,day)!=dow do day-=1 end while
printf(1,"%4d-%02d-%02d\n",{year,month,day})
end procedure
 
procedure last_day_of_month(integer year, integer dow)
integer doy
timedate first = {year,1,1,0,0,0,0,0}
-- start by finding the 1st of the next month, less 1
for i=1 to 11 do
doy = day_of_year(year,i+1,1)-1
showlast(dow,doy,first)
end for
-- do December separately, as 1st would be next year
doy = day_of_year(year,12,31)
showlast(dow,doy,first)
end procedure
last_day_of_month(2012,FRIDAY)
Output:
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28


PHP[edit]

PHP is generally used for web apps, so I am not implementing the command-line component of this task.

<?php
function last_friday_of_month($year, $month) {
$day = 0;
while(True) {
$last_day = mktime(0, 0, 0, $month+1, $day, $year);
if (date("w", $last_day) == 5) {
return date("Y-m-d", $last_day);
}
$day -= 1;
}
}
 
function print_last_fridays_of_month($year) {
foreach(range(1, 12) as $month) {
echo last_friday_of_month($year, $month), "<br>";
}
}
 
date_default_timezone_set("GMT");
$year = 2012;
print_last_fridays_of_month($year);
?>
Output:
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

PicoLisp[edit]

(de lastFridays (Y)
(for M 12
(prinl
(dat$
(find '((D) (= "Friday" (day D)))
(mapcar '((D) (date Y M D)) `(range 31 22)) )
"-" ) ) ) )

Test:

: (lastFridays 2012)
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

Pike[edit]

int(0..1) last_friday(object day)
{
return day->week_day() == 5 &&
day->month_day() > day->month()->number_of_days()-7;
}
 
int main(int argc, array argv)
{
array days = filter(Calendar.Year((int)argv[1])->months()->days()[*], last_friday);
write("%{%s\n%}", days->format_ymd());
return 0;
}

PL/I[edit]

 
Fridays: procedure (year) options (main); /* 8 January 2013 */
declare year character (4) varying;
declare start fixed binary (31);
declare months fixed decimal (2) initial (0);
declare (current_month, month_one_week_hence) character (2);
 
put list ('Last Fridays in each month for the year ' || year || ':' );
start = days('0101' || year, 'DDMMYYYY');
/* Find first Friday */
do while (weekday(start) ^= 6); start = start + 1; end;
 
do until (months=12);
current_month = substr (daystodate(start, 'MMDDYYYY'), 1, 2 );
month_one_week_hence = substr (daystodate(start+7, 'MMDDYYYY'), 1, 2 );
if current_month ^= month_one_week_hence then
do;
months = months + 1;
put skip list (daystodate(start, 'DDMmmYYYY'));
end;
start = start + 7;
end;
end Fridays;
 

The command: FRIDAYS /2008 produces:

Last Fridays in each month for the year 2008:
25Jan2008 
29Feb2008 
28Mar2008 
25Apr2008 
30May2008 
27Jun2008 
25Jul2008 
29Aug2008 
26Sep2008 
31Oct2008 
28Nov2008 
26Dec2008
Output:
for 2013:
Last Fridays in each month for the year 2013: 
25Jan2013 
22Feb2013 
29Mar2013 
26Apr2013 
31May2013 
28Jun2013 
26Jul2013 
30Aug2013 
27Sep2013 
25Oct2013 
29Nov2013 
27Dec2013

PowerShell[edit]

 
function last-dayofweek {
param(
[Int][ValidatePattern("[1-9][0-9][0-9][0-9]")]$year,
[String][validateset('Sunday','Monday','Tuesday','Wednesday','Thursday','Friday','Saturday')]$dayofweek
)
$date = (Get-Date -Year $year -Month 1 -Day 1)
while($date.DayOfWeek -ne $dayofweek) {$date = $date.AddDays(1)}
while($date.year -eq $year) {
if($date.Month -ne $date.AddDays(7).Month) {$date.ToString("yyyy-dd-MM")}
$date = $date.AddDays(7)
}
}
last-dayofweek 2012 "Friday"
 

Output:

2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

Python[edit]

import calendar
c=calendar.Calendar()
fridays={}
year=raw_input("year")
for item in c.yeardatescalendar(int(year)):
for i1 in item:
for i2 in i1:
for i3 in i2:
if "Fri" in i3.ctime() and year in i3.ctime():
month,day=str(i3).rsplit("-",1)
fridays[month]=day
 
for item in sorted((month+"-"+day for month,day in fridays.items()),
key=lambda x:int(x.split("-")[1])):
print item

Using reduce

import calendar
c=calendar.Calendar()
fridays={}
year=raw_input("year")
add=list.__add__
for day in reduce(add,reduce(add,reduce(add,c.yeardatescalendar(int(year))))):
 
if "Fri" in day.ctime() and year in day.ctime():
month,day=str(day).rsplit("-",1)
fridays[month]=day
 
for item in sorted((month+"-"+day for month,day in fridays.items()),
key=lambda x:int(x.split("-")[1])):
print item

using itertools

import calendar
from itertools import chain
f=chain.from_iterable
c=calendar.Calendar()
fridays={}
year=raw_input("year")
add=list.__add__
 
for day in f(f(f(c.yeardatescalendar(int(year))))):
 
if "Fri" in day.ctime() and year in day.ctime():
month,day=str(day).rsplit("-",1)
fridays[month]=day
 
for item in sorted((month+"-"+day for month,day in fridays.items()),
key=lambda x:int(x.split("-")[1])):
print item

R[edit]

year = commandArgs(T)
d = as.Date(paste0(year, "-01-01"))
fridays = d + seq(by = 7,
(5 - as.POSIXlt(d)$wday) %% 7,
364 + (months(d + 30 + 29) == "February"))
message(paste(collapse = "\n", fridays[tapply(
seq_along(fridays), as.POSIXlt(fridays)$mon, max)]))

Racket[edit]

 
#lang racket
(require srfi/19 math)
 
(define (days-in-month m y)
(define lengths #(0 31 #f 31 30 31 30 31 31 30 31 30 31))
(define d (vector-ref lengths m))
(or d (days-in-feb y)))
 
(define (leap-year? y)
(and (divides? 4 y)
(or (not (divides? 100 y))
(divides? 400 y))))
 
(define (days-in-feb y)
(if (leap-year? y) 29 28))
 
(define (last-day-in-month m y)
(make-date 0 0 0 0 (days-in-month m y) m y 0))
 
(define (week-day date)
(define days #(sun mon tue wed thu fri sat))
(vector-ref days (date-week-day date)))
 
(define (last-fridays y)
(for/list ([m (in-range 1 13)])
(prev-friday (last-day-in-month m y))))
 
(define 24hours (make-time time-duration 0 (* 24 60 60)))
 
(define (prev-day d)
(time-utc->date
(subtract-duration
(date->time-utc d) 24hours)))
 
(define (prev-friday d)
(if (eq? (week-day d) 'fri)
d
(prev-friday (prev-day d))))
 
(for ([d (last-fridays 2012)])
(displayln (~a (date->string d "~a ~d ~b ~Y"))))
 
Output:
Fri 27 Jan 2012
Fri 24 Feb 2012
Fri 30 Mar 2012
Fri 27 Apr 2012
Fri 25 May 2012
Fri 29 Jun 2012
Fri 27 Jul 2012
Fri 31 Aug 2012
Fri 28 Sep 2012
Fri 26 Oct 2012
Fri 30 Nov 2012
Fri 28 Dec 2012

REBOL[edit]

The longer version:

leap-year?:  function [year] [to-logic attempt [to-date reduce [29 2 year]]]
 
days-in-feb: function [year] [either leap-year? year [29] [28]]
 
days-in-month: function [month year] [
do pick [31 (days-in-feb year) 31 30 31 30 31 31 30 31 30 31] month
]
 
last-day-of-month: function [month year] [
to-date reduce [year month days-in-month month year]
]
 
last-weekday-of-month: function [weekday month year] [
d: last-day-of-month month year
while [d/weekday != weekday] [d/day: d/day - 1]
d
]
 
last-friday-of-month: function [month year] [last-weekday-of-month 5 month year]
 
year: to-integer input
repeat month 12 [print last-friday-of-month month year]
 
Output:
rebol last-fridays.reb <<< 2012
27-Jan-2012
24-Feb-2012
30-Mar-2012
27-Apr-2012
25-May-2012
29-Jun-2012
27-Jul-2012
31-Aug-2012
28-Sep-2012
26-Oct-2012
30-Nov-2012
28-Dec-2012

A shorter version:

last-fridays-of-year: function [year] [
collect [
repeat month 12 [
d: to-date reduce [1 month year]
d/month: d/month + 1 ; start of next month
until [d/day: d/day - 1 d/weekday = 5] ; go backwards until find a Friday
keep d
]
]
]
 
foreach friday last-fridays-of-year to-integer input [print friday]
 

NB. See "Find the last Sunday of each month" Rosetta for alternative (even more succinct) solution

REXX[edit]

This REXX program will find the last day-of-week (for any day) of all the months for any year.
It wasn't optimized just to find a particular day-of-week.

The documentation for the lastDOW function   (used in the REXX program below):

      ╔════════════════════════════════════════════════════════════════════╗
      ║ lastDOW:  procedure to return the date of the  last day─of─week of ║
      ║           any particular month  of any particular year.            ║
      ║                                                                    ║
      ║ The  day─of─week  must be specified (it can be in any case,        ║
      ║ (lower─/mixed─/upper─case)  as an English name of the spelled day  ║
      ║ of the week,   with a minimum length that causes no ambiguity.     ║
      ║ I.E.:   W  for Wednesday,   Sa  for Saturday,   Su  for Sunday ... ║
      ║                                                                    ║
      ║ The month can be specified as an integer   1 ──► 12                ║
      ║    1=January     2=February     3=March     ...     12=December    ║
      ║ or the English  name  of the month,  with a minimum length that    ║
      ║ causes no ambiguity.    I.E.:  Jun  for June,   D  for December.   ║
      ║ If omitted  [or an asterisk(*)],  the current month is used.       ║
      ║                                                                    ║
      ║ The year is specified as an integer or just the last two digits    ║
      ║ (two digit years are assumed to be in the current century,  and    ║
      ║ there is no windowing for a two─digit year).                       ║
      ║ If omitted  [or an asterisk(*)],  the current year is used.        ║
      ║ Years < 100   must be specified with  (at least 2)  leading zeroes.║
      ║                                                                    ║
      ║ Method used:  find the "day number" of the 1st of the next month   ║
      ║ then subtract one  (this gives the "day number" of the last day of ║
      ║ the month,  bypassing the leapday mess).   The last day─of─week is ║
      ║ then obtained straightforwardly,   or  via subtraction.            ║
      ╚════════════════════════════════════════════════════════════════════╝
/*REXX program displays the dates of the  last Fridays of each month for any given year.*/
parse arg yyyy
do j=1 for 12
say lastDOW('Friday', j, yyyy) /*find last Friday for the Jth month.*/
end /*j*/
exit /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
lastDOW: procedure; arg dow .,mm .,yy .; parse arg a.1,a.2,a.3 /*DOW = day of week*/
if mm=='' | mm=='*' then mm=left( date('U'), 2) /*use default month*/
if yy=='' | yy=='*' then yy=left( date('S'), 4) /*use default year */
if length(yy)==2 then yy=left( date('S'), 2)yy /*append century. */
/*Note mandatory leading blank in strings below*/
$=" Monday TUesday Wednesday THursday Friday SAturday SUnday"
!=" JAnuary February MARch APril MAY JUNe JULy AUgust September October November December"
upper $ ! /*uppercase strings*/
if dow=='' then call .er "wasn't specified",1
if arg()>3 then call .er 'arguments specified',4
 
do j=1 for 3 /*any plural args ?*/
if words(arg(j))>1 then call .er 'is illegal:',j
end
 
dw=pos(' 'dow,$) /*find day-of-week*/
if dw==0 then call .er 'is invalid:',1
if dw\==lastpos(' 'dow,$) then call .er 'is ambigious:',1
 
if datatype(mm,'M') then /*is MM alphabetic?*/
do
m=pos(' 'mm,!) /*maybe its good...*/
if m==0 then call .er 'is invalid:',1
if m\==lastpos(' 'mm,!) then call .er 'is ambigious:',2
mm=wordpos( word( substr(!, m), 1), !) - 1 /*now, use true Mon*/
end
 
if \datatype(mm,'W') then call .er "isn't an integer:",2
if \datatype(yy,'W') then call .er "isn't an integer:",3
if mm<1 | mm>12 then call .er "isn't in range 1──►12:",2
if yy=0 then call .er "can't be 0 (zero):",3
if yy<0 then call .er "can't be negative:",3
if yy>9999 then call .er "can't be > 9999:",3
 
tdow=wordpos(word(substr($,dw),1),$)-1 /*target DOW, 0──►6*/
/*day# of last dom.*/
_=date('B',right(yy+(mm=12),4)right(mm//12+1,2,0)"01",'S')-1
?=_ // 7 /*calc. DOW, 0──►6*/
if ?\==tdow then _=_ - ? - 7 + tdow + 7 * (?>tdow) /*not DOW? Adjust.*/
return date('weekday', _, "B") date(, _, 'B') /*return the answer*/
/*──────────────────────────────────────────────────────────────────────────────────────*/
.er: arg ,_; say; say '***error*** (in LASTDOW)'; say /*tell error, and */
say word('day-of-week month year excess',arg(2)) arg(1) a._
say; exit 13 /*... then exit. */

output   when using the following input:   2012     or     12

Friday 27 Jan 2012
Friday 24 Feb 2012
Friday 30 Mar 2012
Friday 27 Apr 2012
Friday 25 May 2012
Friday 29 Jun 2012
Friday 27 Jul 2012
Friday 31 Aug 2012
Friday 28 Sep 2012
Friday 26 Oct 2012
Friday 30 Nov 2012
Friday 28 Dec 2012

Ring[edit]

 
see "What year to calculate (yyyy) : "
give year
see "Last Friday in " + year + " are on :" + nl
month = list(12)
mo = [4,0,0,3,5,1,3,6,2,4,0,2]
mon = [31,28,31,30,31,30,31,31,30,31,30,31]
if year < 2100 leap = year - 1900 else leap = year - 1904 ok
m = ((year-1900)%7) + floor(leap/4) % 7
for n = 1 to 12
month[n] = (mo[n] + m) % 7
next
for n = 1 to 12
for i = (mon[n] - 6) to mon[n]
if year%4 = 0 and n<3
x = (month[n] + i) % 7 - 1
else x = (month[n] + i) % 7 ok
if n < 10 strn = "0" + string(n) else strn = string(n) ok
if x = 2 see year + "-" + strn + "-" + string(i) + nl ok
next
next
 
 

Output:

What year to calculate (yyyy) : 2012
Last Fridays in 2012 are on :
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

Ruby[edit]

require 'date'
 
def last_friday(year, month)
# Last day of month: Date.new interprets a negative number as a relative month/day from the end of year/month.
d = Date.new(year, month, -1)
d -= (d.wday - 5) % 7 # Subtract days after Friday.
end
 
year = Integer(ARGV.shift)
(1..12).each {|month| puts last_friday(year, month)}

Friday is d.wday == 5; the expression (d.wday - 5) % 7 counts days after Friday.

Output:
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

Or get the last day of the month and go to the previous day until it's a Friday.

require 'date'
 
def last_friday(year, month)
d = Date.new(year, month, -1)
d = d.prev_day until d.friday?
d
end
 

Run BASIC[edit]

input "Year:";yr
dayOne$ = "01-01-";yr
n1 = date$(dayOne$)
for i = 1 to 12
n1 = n1 + 26
m1$ = left$(date$(n1),2)
while m1$ = left$(date$(n1),2) ' find end of month
n1 = n1 + 1
wend
n1 = n1 -1
while (n1 Mod 7) <> 3 ' find Friday
n1 = n1 - 1
wend
print date$(n1) ' print last Friday's date
next i
Year:?2013
01/25/2013
02/22/2013
03/29/2013
04/26/2013
05/31/2013
06/28/2013
07/26/2013
08/30/2013
09/27/2013
10/25/2013
11/29/2013
12/27/2013

Scala[edit]

import java.util.Calendar
import java.text.SimpleDateFormat
 
object Fridays {
 
def lastFridayOfMonth(year:Int, month:Int)={
val cal=Calendar.getInstance
cal.set(Calendar.YEAR, year)
cal.set(Calendar.MONTH, month)
cal.set(Calendar.DAY_OF_WEEK, Calendar.FRIDAY)
cal.set(Calendar.DAY_OF_WEEK_IN_MONTH, -1)
cal.getTime
}
 
def fridaysOfYear(year:Int)=for(month <- 0 to 11) yield lastFridayOfMonth(year, month)
 
def main(args:Array[String]){
val year=args(0).toInt
val formatter=new SimpleDateFormat("yyyy-MMM-dd")
fridaysOfYear(year).foreach{date=>
println(formatter.format(date))
}
}
}
Output:
2012-Jan-27
2012-Feb-24
2012-Mrz-30
2012-Apr-27
2012-Mai-25
2012-Jun-29
2012-Jul-27
2012-Aug-31
2012-Sep-28
2012-Okt-26
2012-Nov-30
2012-Dez-28

Seed7[edit]

Uses the libraries time.s7i and duration.s7i. Applicable to any day of the week, cf. [[2]].

$ include "seed7_05.s7i";
include "time.s7i";
include "duration.s7i";
 
const proc: main is func
local
var integer: weekday is 1; # 1 for monday, 2 for tuesday, and so on up to 7 for sunday.
var integer: year is 0;
var integer: month is 1;
var time: aDate is time.value;
var time: selected is time.value;
begin
if length(argv(PROGRAM)) <> 2 then
writeln("usage: lastWeekdayInMonth weekday year");
writeln(" weekday: 1 for monday, 2 for tuesday, and so on up to 7 for sunday.");
else
weekday := integer parse (argv(PROGRAM)[1]);
year := integer parse (argv(PROGRAM)[2]);
for month range 1 to 12 do
aDate := date(year, month, 1);
while aDate.month = month do
if dayOfWeek(aDate) = weekday then
selected := aDate;
end if;
aDate +:= 1 . DAYS;
end while;
writeln(strDate(selected));
end for;
end if;
end func;
Output:
when called with s7 rosetta/lastWeekdayInMonth 5 2013:
2013-01-25
2013-02-22
2013-03-29
2013-04-26
2013-05-31
2013-06-28
2013-07-26
2013-08-30
2013-09-27
2013-10-25
2013-11-29
2013-12-27

Sidef[edit]

Translation of: Perl
require('DateTime');
var (year=2015) = ARGV»to_i»()...;
 
range(1, 12).each { |month|
var dt = %s'DateTime'.last_day_of_month(year => year, month => month);
while (dt.day_of_week != 5) {
dt.subtract(days => 1);
};
say dt.ymd;
}
Output:
$ sidef lastfriday.sf 2012
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

Smalltalk[edit]

 
Pharo Smalltalk
 
[ :yr | | firstDay firstFriday |
firstDay := Date year: yr month: 1 day: 1.
firstFriday := firstDay addDays: (6 - firstDay dayOfWeek).
(0 to: 53)
collect: [ :each | firstFriday addDays: (each * 7) ]
thenSelect: [ :each |
(((Date daysInMonth: each monthIndex forYear: yr) - each dayOfMonth) <= 6) and: [ each year = yr ] ] ]
 
Output:
Send value: 2012 to the above block to return an array: 
(27 January 2012 24 February 2012 30 March 2012 27 April 2012 25 May 2012 29 June 2012 27 July 2012 31 August 2012 28 September 2012 26 October 2012 30 November 2012 28 December 2012)

SQL[edit]

 
SELECT to_char( next_day( last_day( add_months( to_date(
 :yr||'01','yyyymm' ),level-1))-7,'Fri') ,'yyyy-mm-dd Dy') lastfriday
FROM dual
CONNECT BY level <= 12;
 
LASTFRIDAY
-----------------------
2012-01-27 Fri
2012-02-24 Fri
2012-03-30 Fri
2012-04-27 Fri
2012-05-25 Fri
2012-06-29 Fri
2012-07-27 Fri
2012-08-31 Fri
2012-09-28 Fri
2012-10-26 Fri
2012-11-30 Fri
2012-12-28 Fri

12 rows selected.

Tcl[edit]

package require Tcl 8.5
set year [lindex $argv 0]
foreach dm {02/1 03/1 04/1 05/1 06/1 07/1 08/1 09/1 10/1 11/1 12/1 12/32} {
# The [clock scan] code is unhealthily clever; use it for our own evil purposes
set t [clock scan "last friday" -base [clock scan $dm/$year -gmt 1] -gmt 1]
# Print the interesting part
puts [clock format $t -format "%Y-%m-%d" -gmt 1]
}

Sample execution:

$ tclsh8.5 lastfri.tcl 2012
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

TUSCRIPT[edit]

 
$$ MODE TUSCRIPT
year=2012
LOOP month=1,12
LOOP day=31,22,-1
dayofweek=DATE (number,day,month,year,nummer)
IF (dayofweek==5) THEN
PRINT year,"-",month,"-",day
EXIT
ENDIF
ENDLOOP
ENDLOOP
 
Output:
2012-1-27
2012-2-24
2012-3-30
2012-4-27
2012-5-25
2012-6-29
2012-7-27
2012-8-31
2012-9-28
2012-10-26
2012-11-30
2012-12-28

UNIX Shell[edit]

Using ncal. Will switch to Julian calender as ncal sees fit, and will not calculate past year 9999 (chances are you'll be too dead by then to worry about weekends anyway).

#!/bin/sh
 
if [ -z $1 ]; then exit 1; fi
 
# weed out multiple erros due to bad year
ncal 1 $1 > /dev/null && \
for m in 01 02 03 04 05 06 07 08 09 10 11 12; do
echo $1-$m-`ncal $m $1 | grep Fr | sed 's/.* \([0-9]\)/\1/'`
done


For systems without ncal:

#!/bin/sh
 
# usage: last_fridays [ year]
 
year=${1:-`date +%Y`} # default to current year
month=1
while [ 12 -ge $month ]; do
# Ensure 2 digits: if we try to strip off 2 characters but it still
# looks the same, that means there was only 1 char, so we'll pad it.
[ "$month" = "${month%??}" ] && month=0$month
 
cal $month $year | awk '{print $6}' | grep . | tail -1 \
| sed "s@^@$year-$month-@"
 
# Strip leading zeros to avoid octal interpretation
month=$(( 1 + ${month#0} ))
done


Using date --date from GNU date??? This code is not portable.

#!/bin/sh
 
# Free code, no limit work
# $Id: lastfridays,v 1.1 2011/11/10 00:48:16 gilles Exp gilles $
 
# usage :
# lastfridays 2012 # prints last fridays of months of year 2012
 
debug=${debug:-false}
#debug=true
 
epoch_year_day() {
#set -x
x_epoch=`expr ${2:-0} '*' 86400 + 43200`
date --date="${1:-1970}-01-01 UTC $x_epoch seconds" +%s
}
 
year_of_epoch() {
date --date="1970-01-01 UTC ${1:-0} seconds" +%Y
}
day_of_epoch() {
LC_ALL=C date --date="1970-01-01 UTC ${1:-0} seconds" +%A
}
date_of_epoch() {
date --date="1970-01-01 UTC ${1:-0} seconds" "+%Y-%m-%d"
}
month_of_epoch() {
date --date="1970-01-01 UTC ${1:-0} seconds" "+%m"
}
 
last_fridays() {
year=${1:-2012}
 
next_year=`expr $year + 1`
$debug && echo "next_year $next_year"
 
current_year=$year
day=0
previous_month=01
 
while test $current_year != $next_year; do
 
$debug && echo "day $day"
 
current_epoch=`epoch_year_day $year $day`
$debug && echo "current_epoch $current_epoch"
 
current_year=`year_of_epoch $current_epoch`
 
current_day=`day_of_epoch $current_epoch`
$debug && echo "current_day $current_day"
 
test $current_day = 'Friday' && current_friday=`date_of_epoch $current_epoch`
$debug && echo "current_friday $current_friday"
 
current_month=`month_of_epoch $current_epoch`
$debug && echo "current_month $current_month"
 
# Change of month => previous friday is the last of month
test "$previous_month" != "$current_month" \
&& echo $previous_friday
 
previous_month=$current_month
previous_friday=$current_friday
day=`expr $day + 1`
done
}
 
# main
last_fridays ${1:-2012}

Sample execution:

lastfridays 2012
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

Visual FoxPro[edit]

 
*!* OOP implementaion
LOCAL lnYear As Integer, oCalc As fricalc
CLEAR
lnYear = VAL(INPUTBOX("Year", "Year"))
oCalc = NEWOBJECT("fricalc")
oCalc.LastFriday(lnYear)
 
DEFINE CLASS fricalc As Session
DataSession = 2 && Private
 
PROCEDURE Init
*!* These date settings are private to this class
SET DATE YMD
SET CENTURY ON
SET MARK TO "-"
ENDPROC
 
FUNCTION LastFriday(tnYear As Integer) As VOID
LOCAL i As Integer, ldDate As Date
CLEAR
? "Last Fridays in the year " + TRANSFORM(tnYear)
FOR i = 1 TO 12
ldDate = DATE(tnYear, i, 1) && 1st of month
ldDate = GOMONTH(ldDate, 1) - 1 && last day of month
*!* Use the built in function to return the day of the week
*!* 6 is Friday
DO WHILE DOW(ldDate) # 6
ldDate = ldDate - 1
ENDDO
? ldDate
ENDFOR
ENDFUNC
 
ENDDEFINE
 

XPL0[edit]

include c:\cxpl\codes; \intrinsic 'code' declarations
 
func WeekDay(Year, Month, Day); \Return day of week (0=Sun, 1=Mon ... 6=Sat)
int Year, Month, Day; \works for years from 1583 onward
[if Month<=2 then [Month:= Month+12; Year:= Year-1];
return rem((Day-1 + (Month+1)*26/10 + Year + Year/4 + Year/100*6 + Year/400)/7);
];
 
int Year, Month, LastDay, WD;
[Year:= IntIn(8); \from command line
for Month:= 1 to 12 do
[LastDay:= WeekDay(Year, Month+1, 1) - WeekDay(Year, Month, 28);
if LastDay < 0 then LastDay:= LastDay + 7;
LastDay:= LastDay + 27; \ = number of days in Month
WD:= WeekDay(Year, Month, LastDay);
WD:= WD - 5;
if WD < 0 then WD:= WD + 7;
LastDay:= LastDay - WD;
IntOut(0, Year); ChOut(0, ^-);
if Month < 10 then ChOut(0, ^0); IntOut(0, Month); ChOut(0, ^-);
IntOut(0, LastDay); CrLf(0);
];
]
Output:
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28

zkl[edit]

Gregorian calendar

var [const] D=Time.Date;
fcn lastDay(y,_d){[1..12].pump(Console.println,
'wrap(m){D.daysInMonth(y,m) :
[_..1,-1].pump(Void,'wrap(d){
D.weekDay(y,m,d) :
if (_==_d)return(Void.Stop,"%d-%02d-%02d".fmt(y,m,d))
})
})
}
lastDay(2012,D.Friday)

For each month in year y, count back from the last day in the month until a Friday is found and print that date. A pump is a loop over a sequence and Void.Stop stops the pump with a value. The first parameter to a pump is the sink. All the imperative loop constructs are available but I didn't feel like using them. A wrap is a function closure over unknown values in the function, necessary because functions are not lexically scoped.

Output:
2012-01-27
2012-02-24
2012-03-30
2012-04-27
2012-05-25
2012-06-29
2012-07-27
2012-08-31
2012-09-28
2012-10-26
2012-11-30
2012-12-28