Remove ambiguity in the time display format in core, switches to using 24hr notation where am/pm isn't specified.

* `H:i - 09:54`
* `g:i a - 9:54 am`
* `F j, Y - January 3, 2015`

These shouldn't be used without a/A (am/AM)
* `h:i - 01:23`
* `G:i - 1:23`

Props iseulde. Fixes #31121

Built from https://develop.svn.wordpress.org/trunk@31862


git-svn-id: http://core.svn.wordpress.org/trunk@31841 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/options-general.php

@@ -18,7 +18,7 @@ if ( ! current_user_can( 'manage_options' ) )
 $title = __('General Settings');
 $parent_file = 'options-general.php';
 /* translators: date and time format for exact current time, mainly about timezones, see http://php.net/date */
-$timezone_format = _x('Y-m-d G:i:s', 'timezone date format');
+$timezone_format = _x('Y-m-d H:i:s', 'timezone date format');
 
 /**
  * Display JavaScript on the page.