Index: misc/timezone.js
===================================================================
RCS file: /cvs/drupal/drupal/misc/timezone.js,v
retrieving revision 1.7
diff -u -9 -p -r1.7 timezone.js
--- misc/timezone.js	31 Aug 2009 05:51:08 -0000	1.7
+++ misc/timezone.js	13 Apr 2010 18:36:36 -0000
@@ -5,19 +5,20 @@
  * Set the client's system time zone as default values of form fields.
  */
 Drupal.behaviors.setTimezone = {
   attach: function (context, settings) {
     $('select.timezone-detect', context).once('timezone', function () {
       var dateString = Date();
       // In some client environments, date strings include a time zone
       // abbreviation, between 3 and 5 letters enclosed in parentheses,
       // which can be interpreted by PHP.
-      var matches = dateString.match(/\(([A-Z]{3,5})\)/);
+      var abbreviationPattern = /\(([A-Z]{3,5})\)/;
+      var matches = dateString.match(abbreviationPattern);
       var abbreviation = matches ? matches[1] : 0;
 
       // For all other client environments, the abbreviation is set to "0"
       // and the current offset from UTC and daylight saving time status are
       // used to guess the time zone.
       var dateNow = new Date();
       var offsetNow = dateNow.getTimezoneOffset() * -60;
 
       // Use January 1 and July 1 as test dates for determining daylight
@@ -31,18 +32,30 @@ Drupal.behaviors.setTimezone = {
       // If the offset from UTC is identical on January 1 and July 1,
       // assume daylight saving time is not used in this time zone.
       if (offsetJan == offsetJul) {
         isDaylightSavingTime = '';
       }
       // If the maximum annual offset is equivalent to the current offset,
       // assume daylight saving time is in effect.
       else if (Math.max(offsetJan, offsetJul) == offsetNow) {
         isDaylightSavingTime = 1;
+
+        // On some client systems, the same time zone abbreviation is used for
+        // both offsets, e.g. 'CET' (Central European Time) is used both in
+        // January and July, even though the official abbreviation during
+        // daylight saving time is CEST (Central European Summer Time). This
+        // confuses PHP's timezone_name_from_abbr(), so omit the abbreviation
+        // during daylight saving time.
+        var matchesJan = dateJan.toString().match(abbreviationPattern);
+        var matchesJul = dateJul.toString().match(abbreviationPattern);
+        if (matchesJan && matchesJul && matchesJan[1] == matchesJul[1]) {
+          abbreviation = '';
+        }
       }
       // Otherwise, assume daylight saving time is not in effect.
       else {
         isDaylightSavingTime = 0;
       }
 
       // Submit request to the system/timezone callback and set the form field
       // to the response time zone. The client date is passed to the callback
       // for debugging purposes. Submit a synchronous request to avoid database