Changeset 18514 in webkit

Timestamp:

Jan 1, 2007, 8:19:35 PM (18 years ago)

Author:

ddkilzer

Message:

JavaScriptCore:

Reviewed by Darin.

• fix ​http://bugs.webkit.org/show_bug.cgi?id=12057 REGRESSION: JavaScript Date Is One Day In The Future in GMT time zone

Because Mac OS X returns geographically and historically accurate time zone information,
converting Jan 02, 1970 12:00:00 AM to local time then subtracting 24 hours did not work
in GMT (London - England) since it was in BST (+0100) all year in 1970[1]. Instead, the
UTC offset is calculated by converting Jan 01, 2000 12:00:00 AM to local time then
subtracting that from the same date in UTC.

[1] ​http://en.wikipedia.org/wiki/British_Summer_Time

• kjs/DateMath.cpp: (KJS::getUTCOffset): Updated UTC offset calculation. (KJS::getDSTOffset): Improved comment.

Location:

trunk/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• kjs/DateMath.cpp (modified) (3 diffs)

trunk/JavaScriptCore/ChangeLog

@@ +1 @@
+2007-01-01  David Kilzer  <ddkilzer@webkit.org>
+
+        Reviewed by Darin.
+
+        - fix http://bugs.webkit.org/show_bug.cgi?id=12057
+          REGRESSION: JavaScript Date Is One Day In The Future in GMT time zone
+
+        Because Mac OS X returns geographically and historically accurate time zone information,
+        converting Jan 02, 1970 12:00:00 AM to local time then subtracting 24 hours did not work
+        in GMT (London - England) since it was in BST (+0100) all year in 1970[1].  Instead, the
+        UTC offset is calculated by converting Jan 01, 2000 12:00:00 AM to local time then
+        subtracting that from the same date in UTC.
+
+        [1] http://en.wikipedia.org/wiki/British_Summer_Time
+
+        * kjs/DateMath.cpp:
+        (KJS::getUTCOffset): Updated UTC offset calculation.
+        (KJS::getDSTOffset): Improved comment.
+
 2006-12-31  David Kilzer  <ddkilzer@webkit.org>
 

trunk/JavaScriptCore/kjs/DateMath.cpp

@@ -1 +1 @@
 /*
  * Copyright (C) 1999-2000 Harri Porten (porten@kde.org)
- * Copyright (C) 2006 Apple Computer
+ * Copyright (C) 2006-2007 Apple Computer
  *
  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
@@ -300 +300 @@
 
         memset(&localt, 0, sizeof(localt));
-        
-        // get the difference between this time zone and GMT 
-        localt.tm_mday = 2;
-        localt.tm_year = 70;
-
-        utcOffset = mktime(&localt) - (hoursPerDay * secondsPerHour);
-        utcOffset *= -msPerSecond;
+
+        // get the difference between this time zone and UTC on Jan 01, 2000 12:00:00 AM
+        localt.tm_mday = 1;
+        localt.tm_year = 100;
+        utcOffset = 946684800.0 - mktime(&localt);
+
+        utcOffset *= msPerSecond;
 
         utcOffsetInitialized = true;
@@ -359 +359 @@
     // determining DST.  For this reason we shift years that localtime can handle but would
     // return historically accurate information.
-    
-    //if before 2000 or after 2038
+
+    // if before Jan 01, 2000 12:00:00 AM UTC or after Jan 01, 2038 12:00:00 AM UTC
     if (ms < 946684800000.0 || ms > 2145916800000.0) {
         int year;