Hello Perl gurus,

I did read few threads on PerMonks before posting this question here.

Friday 01-01-2016, starts and ends the week. Inspite of this being the first day in the first week of year, the week indicated by DateTime is 53.

I also tried using localtime function and evantually calculating week# based of yearday. Although, it returns week 1, the calculation based on yearday, returns week 1 for the week beginning 04/01/2016 - 08/01/2016, which is actually week 2.

cal -w 1 2016 command starts with week 1 and goes on .. finally shows last week of 2016 as week 53, which as per me is correct.

I think most of you would agree that the cal command output is correct.

Question is, how do I get it right in perl ? 

====
#!/usr/bin/env perl

#use 5.012;
use strict;
use warnings;

use DateTime;
use Time::Local;

my $dt = DateTime->new(year => 2016, month => 1, day => 1);

print "DateTIme confirms that 01-01-2016 was a => " . $dt->day_name . 
+"\n";
print "DateTime return the Week no for 01-01-2016 => " . $dt->week . "
+\n";

$dt = DateTime->new(year => 2016, month => 1, day => 4);
print "DateTIme confirms that 04-01-2016 was a => " . $dt->day_name . 
+"\n";
print "DateTime return the Week no for 04-01-2016 => " . $dt->week . "
+\n";

my ($MONTHDAY, $WEEKDAY, $YEARDAY) = (localtime (timelocal(0,0,0,1,0,2
+016)))[3,6,7];
my $WEEKNUM = int($YEARDAY / 7) + 1;

print "using localtime to calculate weekno (01/01/2016) => " . $WEEKNU
+M . "\n";

($MONTHDAY, $WEEKDAY, $YEARDAY) = (localtime (timelocal(0,0,0,4,0,2016
+)))[3,6,7];
$WEEKNUM = int($YEARDAY / 7) + 1;

print "using localtime to calculate weekno (04/01/2016) => " . $WEEKNU
+M . "\n";

print "UNIX system cal command output for 1st month \n";
system("cal -w 1 2016");
===

[download]

Output:

Perl DateTIme confirms that 01-01-2016 was a => Friday
Perl DateTime return the Week no for 01-01-2016 => 53

Perl DateTIme confirms that 04-01-2016 was a => Monday
Perl DateTime return the Week no for 04-01-2016 => 1

using localtime to calculate weekno (01/01/2016) => 1
using localtime to calculate weekno (04/01/2016) => 1

UNIX system cal command output for 1st month

January 2016

Su Mo Tu We Th Fr Sa

1 1 2

2 3 4 5 6 7 8 9

3 10 11 12 13 14 15 16

4 17 18 19 20 21 22 23

5 24 25 26 27 28 29 30

6 31

In reply to Another date question by sshingor

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