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Bug #63970 Wrong year on week calculation from 2012-12-30
Submitted: 2013-01-11 16:31 UTC Modified: 2013-01-12 09:21 UTC
From: obibann at hotmail dot com Assigned:
Status: Not a bug Package: Date/time related
PHP Version: 5.3.20 OS: RedHat EL 6.2
Private report: No CVE-ID: None
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 [2013-01-11 16:31 UTC] obibann at hotmail dot com 
Description:
------------
Set your server on December 30 2012:

date -s "20121230 11:00"

Ask PHP to give you the year and week 52 weeks ago thanks to the code below.
PHP prints "201252" instead of "201201"
No problems from other dates of with another value of week.

Test script:
---------------
date_default_timezone_set("Your/Timezone"); // For me Europe/Paris
echo date("YW",strtotime("-52 week"));

Expected result:
----------------
201201

Actual result:
--------------
201252

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 [2013-01-11 16:34 UTC] obibann at hotmail dot com 
Erratum :

I think it should return "201152"
 [2013-01-11 16:51 UTC] derick@php.net
-Status: Open +Status: Not a bug
 [2013-01-11 16:51 UTC] derick@php.net 
Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php

This is not a bug. "Y" is the real year, where as "o" is the ISO year. The "W" denotes the "ISO Week number" which ties in into the "ISO Year". Please refer to http://en.wikipedia.org/wiki/ISO_week for the back story.

When you run your script with "o" instead of "Y", the answer is the correct "201152":

<?php
date_default_timezone_set("Europe/Paris");
echo date("o-W",strtotime("2012-12-30 11:00 -52 week")), "\n";
?>

Shows:

2011-52
 [2013-01-12 09:21 UTC] obibann at hotmail dot com 
Great !
Thank you very much for this explaination.

Regards
 
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