Find week number within range of dates in Perl

Question

I have a range of dates -- say 2012-01-30 .. 2012-04-06 -- which denote a set of weeks that fall within these dates. These weeks are numbered 1 through 10. Given today's date (for instance, 2012-02-29), I want to be able to get the week number within the range (in this case, 5). How do I achieve this in Perl?

Do your weeks start on Monday? Will the date range always start on a Mondaya and end on a Friday? — Borodin, Jan 28 '12 at 13:37

score 3 · Answer 1 · answered Jan 28 '12 at 12:31

3

Package Time::Piece has strptime method to parse string into a time object and week method to indicate number of the week of the time object.

use Time::Piece;
my @dates = ('2012-01-30', ..., ...., '2012-04-06');

foreach my $strdate (@dates) {
    my $date = Time::Piece->strptime($strdate, "%Y-%m-%d");
    print "Number of week for '$strdate' is " . $date->week . "\n";
}

All you need to do is just to count number of unique weeks in your range.

answered Jan 28 '12 at 12:31

yko

2,710
13
15

This is a neat solution, but requires me to expand the array `@dates` and iterate over it, counting unique weeks. Yes, it works, and doesn't require any non-core modules, but my preference is for a smaller (in terms of code) solution. – Jashank Jeremy Jan 28 '12 at 23:17

score 1 · Accepted Answer · answered Jan 28 '12 at 13:48

1

The value of the end date doesn't make any difference unless you want to incorporate some value checking. The value that you need is week(start date) - week(this date) + 1. I recommend the Date::Calc module for its tidiness and efficiency. The code looks like this

use strict;
use warnings;

use Date::Calc 'Week_Number';

sub week {
  Week_Number(split /-/, $_[0]);
}

print week('2012-02-29') - week('2012-01-30') + 1, "\n";

OUTPUT

answered Jan 28 '12 at 13:48

Borodin

126,100
9
70
144

1

If it matters to the user, Date::Calc isn't a core module, while Time::Piece has been since v5.9.5 – JRFerguson Jan 28 '12 at 14:19
@JRFerguson: Since I already use `Date::Calc`, it's not really an issue. – Jashank Jeremy Jan 28 '12 at 23:14

score 1 · Answer 3 · answered Jan 28 '12 at 19:15

use DateTime qw();
my (undef, $initial_weeknumber) 
    = DateTime->new(year => 2012, month => 1, day => 30)->week;
my (undef, $target_weeknumber)  
    = DateTime->new(year => 2012, month => 2, day => 29)->week;
printf 'We are in week %d of the Jashank epoch.', 
    1 + $target_weeknumber - $initial_weeknumber;

Find week number within range of dates in Perl

3 Answers3