[wp-trac] [WordPress Trac] #34435: get_gmt_from_date() returns incorrect value when 'timezone_tz' is 'Europe/London'

[WordPress Trac]

#34435: get_gmt_from_date() returns incorrect value when 'timezone_tz' is
'Europe/London'
-----------------------------+-----------------------------
 Reporter:  danielbachhuber  |      Owner:
     Type:  defect (bug)     |     Status:  new
 Priority:  normal           |  Milestone:  Awaiting Review
Component:  Date/Time        |    Version:
 Severity:  normal           |   Keywords:
  Focuses:                   |
-----------------------------+-----------------------------
 When I use `wp_insert_post()` to create a post when `timezone_tz` is
 `Europe/London` [https://github.com/danielbachhuber/year-ago-
 today/blob/master/year-ago-today.php#L25-L32 ref], the post gets scheduled
 for the future.

 `$post_date` is established here:
 https://core.trac.wordpress.org/browser/tags/4.3/src/wp-
 includes/post.php#L3272

 Because `$post_date_gmt` isn't supplied, it's set here:
 https://core.trac.wordpress.org/browser/tags/4.3/src/wp-
 includes/post.php#L3292

 However, `get_gmt_from_date()` returns the same value as its supplied,
 when it should return an hour less (as Europe/London respects DST).
 `gmdate()` returns the proper GMT date (one hour less) so the post gets
 forced to `future` [https://core.trac.wordpress.org/browser/tags/4.3/src
 /wp-includes/post.php#L3310 ref]

 Here's debug of `get_gmt_from_date()`:

 {{{
 <?php
 $format = 'Y-m-d H:i:s';
 $string = '2015-10-25 01:23:08';
 $tz = 'Europe/London';
 $datetime = date_create( $string, new DateTimeZone( $tz ) );
 echo $datetime->format( $format ) . PHP_EOL;
 // 2015-10-25 01:23:08
 $datetime->setTimezone( new DateTimeZone( 'UTC' ) );
 echo $datetime->format( $format ) . PHP_EOL;
 // 2015-10-25 01:23:08, but should be 2015-10-25 00:23:08
 }}}

 Is this a bug in PHP, or how we're using `DateTime`? Tested on PHP 5.6.14,
 5.5.9, and 5.5.27

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Ticket URL: <https://core.trac.wordpress.org/ticket/34435>
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