commit b7aacf5f90fa449b521da0535059d945248e04ee
author kmccullo <kmccullo@268f45cc-cd09-0410-ab3c-d52691b4dbfc> Wed Nov 01 20:34:23 2006 +0000
committer kmccullo <kmccullo@268f45cc-cd09-0410-ab3c-d52691b4dbfc> Wed Nov 01 20:34:23 2006 +0000
tree 69e22c060b0c84258b01bb35776f067a9ef11e79
parent f843e353b6a5accbfac8a932f0cf2227e0399ec0

        Reviewed by Brady.

        - Fixes many JavaScriptCore tests in other timezones.  The root problem is that on mac localtime() returns historically accurate information for DST, but the JavaScript spec explicitly states to not take into account historical information but rather to interpolate from valid years.

        * kjs/DateMath.cpp:
        (KJS::equivalentYearForDST):
        (KJS::getDSTOffsetSimple):
        (KJS::getDSTOffset):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@17520 268f45cc-cd09-0410-ab3c-d52691b4dbfc

JavaScriptCore/kjs/DateMath.cpp

diff --git a/JavaScriptCore/kjs/DateMath.cpp b/JavaScriptCore/kjs/DateMath.cpp
index 4a12a9d..f1a0587 100644
--- a/JavaScriptCore/kjs/DateMath.cpp
+++ b/JavaScriptCore/kjs/DateMath.cpp
@@ -66,22 +66,6 @@
     {0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335}
 };
 
-
-/*
- * Years and leap years on which Jan 1 is a Sunday, Monday, etc.
- *
- * yearStartingWith[0][i] is an example non-leap year where
- * Jan 1 appears on Sunday (i == 0), Monday (i == 1), etc.
- *
- * yearStartingWith[1][i] is an example leap year where
- * Jan 1 appears on Sunday (i == 0), Monday (i == 1), etc.
- */
-static int yearStartingWith[2][7] = {
-    {1978, 1973, 1974, 1975, 1981, 1971, 1977},
-    {1984, 1996, 1980, 1992, 1976, 1988, 1972}
-};
-
-
 static inline int daysInYear(int year)
 {
     if (year % 4 != 0)
@@ -298,15 +282,10 @@
  */
 int equivalentYearForDST(int year)
 {
-    int day;
-
-    day = (int) daysFrom1970ToYear(year) + 4;
-    day %= 7;
-
-    if (day < 0)
-        day += 7;
-
-    return yearStartingWith[isLeapYear(year)][day];
+    int difference = 2000 - year;   // Arbitrary year around which most dates equivalence is correct
+    int quotient = difference / 28; // Integer division, no remainder.
+    int product = quotient * 28;
+    return year + product;
 }
 
 /*
@@ -345,6 +324,7 @@
     else if(localTimeSeconds < 0) // Go ahead a day to make localtime work (does not work with 0)
         localTimeSeconds += secondsPerDay;
 
+    //input is UTC so we have to shift back to local time to determine DST thus the + getUTCOffset()
     double offsetTime = (localTimeSeconds * msPerSecond) + getUTCOffset() ;
 
     // Offset from UTC but doesn't include DST obviously
@@ -373,11 +353,14 @@
 // ms is in UTC
 static double getDSTOffset(double ms)
 {
-    /*
-     * If earlier than 1970 or after 2038, potentially beyond the ken of
-     * many OSes, map it to an equivalent year before asking.
-     */
-    if (ms < 0.0 || ms > 2145916800000.0) {
+    // On mac the call to localtime (see getDSTOffsetSimple) will return historically accurate
+    // DST information (e.g. New Zealand did not have DST from 1946 to 1974) however the JavaScript
+    // standard explicitly dictates that historical information should not be considered when
+    // 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 (ms < 946684800000.0 || ms > 2145916800000.0) {
         int year;
         int day;