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Bug #52480 Incorrect difference using DateInterval
Submitted: 2010-07-29 04:49 UTC Modified: 2010-07-30 10:46 UTC
Votes:25
Avg. Score:4.7 ± 0.5
Reproduced:22 of 22 (100.0%)
Same Version:7 (31.8%)
Same OS:5 (22.7%)
From: alex dot joyce at staff dot comcen dot com dot au Assigned: derick
Status: Assigned Package: Date/time related
PHP Version: 5.3.3 OS: Debian 5.0.3
Private report: No CVE-ID:
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 [2010-07-29 04:49 UTC] alex dot joyce at staff dot comcen dot com dot au
Description:
------------
Trying to calculate the month difference between two dates accurately.

Test script:
---------------
<?php

  $date_start = new DateTime('2010-03-01');
  $date_end   = new DateTime('2010-07-29');

  $interval = $date_start->diff($date_end);

  print_r($interval);

Expected result:
----------------
DateInterval Object
(
    [y] => 0
    [m] => 4
    [d] => 29
    [h] => 0
    [i] => 0
    [s] => 0
    [invert] => 0
    [days] => 150
)

Actual result:
--------------
DateInterval Object
(
    [y] => 0
    [m] => 5
    [d] => 0
    [h] => 0
    [i] => 0
    [s] => 0
    [invert] => 0
    [days] => 150
)

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 [2010-07-29 08:27 UTC] rasmus@php.net
-Status: Open +Status: Feedback
 [2010-07-29 08:27 UTC] rasmus@php.net
Don't you mean 4 months and 28 days in the expected results?  7-3=4, 29-1=28
And that is exactly what I get on my Debian box with PHP 5.3.3:


php >   $date_start = new DateTime('2010-03-01');
php >   $date_end   = new DateTime('2010-07-29');
php > 
php >   $interval = $date_start->diff($date_end);
php > 
php >   print_r($interval);
DateInterval Object
(
    [y] => 0
    [m] => 4
    [d] => 28
    [h] => 0
    [i] => 0
    [s] => 0
    [invert] => 0
    [days] => 150
)

Are you using 5.3.3 built from our sources or are you using a Debian-packaged 
version?
 [2010-07-29 08:52 UTC] alex dot joyce at staff dot comcen dot com dot au
-Status: Feedback +Status: Open
 [2010-07-29 08:52 UTC] alex dot joyce at staff dot comcen dot com dot au
28/29, it doesn't matter. I'm only interested in the months.

I've tried:

1) FreeBSD 6, PHP 5.3.2
2) Debian 4, PHP 5.3.2
3) Debian 6, PHP 5.3.2/PHP 5.3.3

I upgraded that last one to submit this bug report, same fault.

All compiled from source.
 [2010-07-29 09:15 UTC] rasmus@php.net
-Status: Open +Status: Feedback
 [2010-07-29 09:15 UTC] rasmus@php.net
I don't see why I can't reproduce it then.  Try adding a call to 
date_default_timezone_set() to the top of your script and work in UTC to 
eliminate local timezone issues.  

  date_default_timezone_set('UTC');
  $date_start = new DateTime('2010-03-01');
  $date_end   = new DateTime('2010-07-29');
  $interval = $date_start->diff($date_end);
  print_r($interval);
 [2010-07-29 09:35 UTC] degeberg@php.net
-Status: Feedback +Status: Open
 [2010-07-29 09:35 UTC] degeberg@php.net
With the timezone set to Europe/Copenhagen, I get the same results as submitter. When set to UTC, I get the same results on Rasmus. This is on Ubuntu 10.04.

daniel@daniel-laptop:~$ php -v
PHP 5.3.4-dev (cli) (built: Jul 29 2010 09:30:24) 
Copyright (c) 1997-2010 The PHP Group
Zend Engine v2.3.0, Copyright (c) 1998-2010 Zend Technologies
 [2010-07-30 01:40 UTC] alex dot joyce at staff dot comcen dot com dot au
Changing the timezone shows a difference.

Australia/Sydney (default): 5 months
UTC: 4 months 28 days
 [2010-07-30 10:46 UTC] derick@php.net
-Status: Open +Status: Assigned -Assigned To: +Assigned To: derick
 [2010-07-30 10:46 UTC] derick@php.net
This is going to be a fun one to fix :-/
 [2011-04-12 16:37 UTC] fischer at wild-east dot de
This happens only when setting a DateTime without the time part or a time below 02:00:00. At least for the 'Europe/Berlin' timezone.
 [2011-06-13 10:51 UTC] petros at rufunka dot com
The problem lies between the last day of February and first day of March. 

At the following example:
$first = new DateTime('2011-03-01');
$second = new DateTime('2011-03-29');
$interval = $second->diff($first);

will get the wrong result.

If I set my timezone to Europe/Stockholm which is +1 GMT then if i set the $first = new DateTime(’2011-03-01 00:59:00′); I still get the wrong result. However an hour value above or equal to +1 ie $first = new DateTime(’2011-03-01 01:00:00′); will give the correct example.

So if you are GMT + 2 you need to have a value above or equal to 2011-03-01 02:00:00.

A quick fix, as mentioned above, is to set your timezone to UTC: date_default_timezone_set(‘UTC’);
and in this case you match the time with the needed in order to get correct results.

Another example with the opposite results is to set your timezone to:
date_default_timezone_set(‘America/Mexico_City’);
$first = new DateTime(’2011-02-28 22:01:00′);
$second = new DateTime(’2011-03-29 03:00:00′);
then the diff will think that you are in the same month.
 [2012-01-31 12:37 UTC] jan at jankramer dot eu
I think this bug is hasn't been fixed yet. 
Below is a reproduction on Ubuntu 11.10 with PHP 5.3.6. 

DateTime Object #1:
(
    [date] => 2011-12-01 00:00:00
    [timezone_type] => 3
    [timezone] => Europe/Amsterdam
)

DateTime Object #2:
(
    [date] => 2012-02-01 00:00:00
    [timezone_type] => 3
    [timezone] => Europe/Amsterdam
)

DateTime Object #3:
(
    [date] => 2011-12-01 12:00:00
    [timezone_type] => 3
    [timezone] => Europe/Amsterdam
)


DateTime Object #4:
(
    [date] => 2012-02-01 12:00:00
    [timezone_type] => 3
    [timezone] => Europe/Amsterdam
)

DateInterval Object #1 & #2
(
    [y] => 0
    [m] => 2
    [d] => 1
    [h] => 0
    [i] => 0
    [s] => 0
    [invert] => 0
    [days] => 62
)

DateInterval Object #3 & #4
(
    [y] => 0
    [m] => 2
    [d] => 0
    [h] => 0
    [i] => 0
    [s] => 0
    [invert] => 0
    [days] => 62
)

The difference in the 'd' attribute is very strange...
 [2012-02-25 12:20 UTC] map at wafriv dot de
I've got the same problem with PHP 5.3.8 on Windows. Like petros at rufunka dot 
com said, there is a difference of 1 hour between Europe/Berlin and UTC.

object(DateTime)[1]
  public 'date' => string '2012-02-25 13:17:52' (length=19)
  public 'timezone_type' => int 3
  public 'timezone' => string 'Europe/Berlin' (length=13)
object(DateTime)[2]
  public 'date' => string '2010-08-07 07:01:25' (length=19)
  public 'timezone_type' => int 3
  public 'timezone' => string 'Europe/Berlin' (length=13)
object(DateInterval)[3]
  public 'y' => int 1
  public 'm' => int 6
  public 'd' => int 18
  public 'h' => int 6
  public 'i' => int 16
  public 's' => int 27
  public 'invert' => int 1
  public 'days' => int 567
object(DateTime)[4]
  public 'date' => string '2012-02-25 12:17:52' (length=19)
  public 'timezone_type' => int 3
  public 'timezone' => string 'UTC' (length=3)
object(DateTime)[1]
  public 'date' => string '2010-08-07 05:01:25' (length=19)
  public 'timezone_type' => int 3
  public 'timezone' => string 'UTC' (length=3)
object(DateInterval)[2]
  public 'y' => int 1
  public 'm' => int 6
  public 'd' => int 18
  public 'h' => int 7
  public 'i' => int 16
  public 's' => int 27
  public 'invert' => int 1
  public 'days' => int 567
 [2014-01-17 13:54 UTC] jimmyraynor at gmail dot com
Ran into this issue with PHP 5.4.17 (cli) (built: Aug 25 2013 02:03:38) 
TZ: date.timezone => America/Santiago
Between dates 2013-09-08 and 2014-01-15
Using OS: Mac Os 10.9
 [2014-01-25 19:24 UTC] kulakov74 at yandex dot ru
I stumbled upon this seemingly wrong behaviour too, while studying the manual, and was all about to add a confirming comment but finally realized the reason behind it. The explanation is that the diff() method first converts its operands to UTC. In cases when the converion changes their months the number of days in the month may change too. For ex. 2010-03-01/2010-07-29 in the very 1st example, when in Europe/Copenhagen, actually converts to 2010-02-28 23:00:00/2010-07-28 23:00:00, hence the difference 5 months 0 days. The conversion explains why the number of hours in the time part matters and should be equal or greater than the timezone offset from UTC in order to avoid the effect. 

Another consequence of the UTC conversion is that the function does not respect any DST shifts (it that matters for you). Using strtotime() for the same dates and subtracting the timestamps might yield a different result (+/-1 hour) if a DST switch is within the dates period. 

I also recommend using a DateTimeZone object for DateTime instead of changing the global TZ for all date functions:

$oTZ=new DateTimeZone('Europe/Moscow');
$DT1=new DateTime('2010-03-01', $oTZ);
 
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