Changeset 17520 in webkit

Timestamp:

Nov 1, 2006 12:34:23 PM (17 years ago)

Author:

kmccullo

Message:

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):

Location:

trunk/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• kjs/DateMath.cpp (modified) (4 diffs)

trunk/JavaScriptCore/ChangeLog

@@ +1 @@
+2006-11-01  Kevin McCullough  <KMcCullough@apple.com>
+
+        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):
+
 2006-10-31  Geoffrey Garen  <ggaren@apple.com>
 

trunk/JavaScriptCore/kjs/DateMath.cpp

@@ -66 +66 @@
     {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)
@@ -299 +283 @@
 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;
 }
 
@@ -346 +325 @@
         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() ;
 
@@ -374 +354 @@
 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;