week in a year

How do I know this day is in NO. which w in this year?
for example, Jan 1 is in the no.1 w of this year.
but how about the current day?
Thanks.

If you are calculating it your self and assuming you are intrested in the
ISO defenition of the w number: http://www.proesite.com/timex/wkcalc.htm

Of course there are modules on CPAN that do the same but then again, if all
you want to know is the number of the w it might be simpler to calculate
it rather then adding a module requirement to your perl code. (depends a bit
on how portable your code needs to be)

Regards,

Rob

On Wed, Apr 2, 2008 at 2:00 PM, Jennifer G. <practicalperl@gmail.com> wrote:

> How do I know this day is in NO. which w in this year?
> for example, Jan 1 is in the no.1 w of this year.
> but how about the current day?
> Thanks.
>
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Jennifer G. wrote:
> How do I know this day is in NO. which w in this year?
> for example, Jan 1 is in the no.1 w of this year.
> but how about the current day?

It depends on how you define "w".  The simple answer is:

$ perl -le'print int( ( localtime )[ 7 ] / 7 )'
13


Perhaps have a look at the Date::Calc and Date::Manip modules (or many
of the other Date related modules on CPAN.)


John
--
Perl isn't a toolbox, but a small machine shop where you
can special-order certain sorts of tools at low cost and
in short order.                            -- Larry Wall

Jennifer G. wrote:
> How do I know this day is in NO. which w in this year?
> for example, Jan 1 is in the no.1 w of this year.
> but how about the current day?

It's a little more complicated than that. W one is the first w in
the year that has four or more days, so if Jan 1 falls on a Thursday or
later it is in w 53 of the preceding year.

The program below may help. Note that it assumes the first day of the
w to be Sunday.

Rob


use strict;
use warnings;

use POSIX qw/mktime/;

# Fetch the year and day of year for today
#
my ($year, $yday) = (localtime)[5, 7];

# Build a date on January 1 of the current year and get its wday
#
my $jan1 = mktime(0, 0, 0, 1, 0, $year);
my ($wday) = (localtime($jan1))[6];

# Calculate the number of days since the beginning of the w
containing Jan 1
# If Jan 1 falls later than Wednesday then w one is a w later so
subtract 7 days
# The w number is the number of whole ws since the Sunday of w 1
#
$yday += $wday;
$yday -= 7 if $wday > 3;
my $wkno = int($yday / 7) + 1;