Bug 836404 - Provide better timezone support in jstests. r=jwalden

--HG--
extra : rebase_source : 11267ba920def4077e843230cddb583cbe8bad6d

js/src/tests/ecma/shell.js

@@ -8,6 +8,7 @@
  * Date functions used by tests in Date suite
  *
  */
+var msPerYear =  31536000000;
 var msPerDay =   86400000;
 var HoursPerDay =  24;
 var MinutesPerHour = 60;
@@ -15,11 +16,19 @@ var SecondsPerMinute = 60;
 var msPerSecond =  1000;
 var msPerMinute =  60000;  // msPerSecond * SecondsPerMinute
 var msPerHour =   3600000; // msPerMinute * MinutesPerHour
-var TZ_DIFF = getTimeZoneDiff();  // offset of tester's timezone from UTC
-var TZ_ADJUST  = TZ_DIFF * msPerHour;
+
 var TZ_PST = -8;  // offset of Pacific Standard Time from UTC
+var TZ_DIFF_RAW = GetRawTimezoneOffset();  // raw offset of tester's timezone from UTC
+var TZ_DIFF = GetTimezoneOffset();  // offset of tester's timezone from UTC
+var PST_DIFF_RAW = TZ_DIFF_RAW - TZ_PST;  // raw offset of tester's timezone from PST
 var PST_DIFF = TZ_DIFF - TZ_PST;  // offset of tester's timezone from PST
+var TZ_ADJUST  = TZ_DIFF_RAW * msPerHour;
 var PST_ADJUST = TZ_PST * msPerHour;
+
+var DST_PERIOD = DaylightSavingPeriod();  // time period when DST is used
+var DST_1970 = DaylightSavingObserved(1970);  // Was DST observed in 1970?
+var DST_1971 = DaylightSavingObserved(1971);  // Was DST observed in 1971?
+
 var TIME_0000  = (function ()
   { // calculate time for year 0
     for ( var time = 0, year = 1969; year >= 0; year-- ) {
@@ -43,9 +52,71 @@ var TIME_NOW = now.valueOf();  //valueOf() is to accurate to the millisecond
  * We calculate the proper number dynamically for any tester. We just
  * have to be careful not to use a date subject to Daylight Savings Time...
  */
-function getTimeZoneDiff()
+function GetRawTimezoneOffset()
 {
-  return -((new Date(2000, 1, 1)).getTimezoneOffset())/60;
+  var t1 = new Date(2000, 1, 1).getTimezoneOffset();
+  var t2 = new Date(2000, 1 + 6, 1).getTimezoneOffset();
+  if ((t1 - t2) >= 0) {
+    // 1) timezone without daylight saving time
+    // 2) northern hemisphere with daylight saving time
+    return -t1 / MinutesPerHour;
+  } else {
+    // 3) southern hemisphere with daylight saving time
+    return -t2 / MinutesPerHour;
+  }
+}
+
+/*
+ * Returns the timezone offset, possibly including daylight saving time.
+ * (This function is only used to obtain the relative timezone offset to PST,
+ * see TZ_DIFF and PST_DIFF in adjustResultArray().)
+ */
+function GetTimezoneOffset()
+{
+  return -(new Date(2000, 1, 1).getTimezoneOffset()) / MinutesPerHour;
+}
+
+/*
+ * Determine when daylight saving time is used in the current timezone.
+ */
+function DaylightSavingPeriod()
+{
+  var t1 = new Date(2000, 1, 1).getTimezoneOffset();
+  var t2 = new Date(2000, 1 + 6, 1).getTimezoneOffset();
+  if (t1 == t2) {
+    // timezone without daylight saving time
+    return 0;
+  } else if ((t1 - t2) > 0) {
+    // northern hemisphere with daylight saving time
+    return 1;
+  } else {
+    // southern hemisphere with daylight saving time
+    return -1;
+  }
+}
+
+/*
+ * Test whether daylight time saving was observed in the supplied year
+ */
+function DaylightSavingObserved(y)
+{
+  var t1 = new Date(y, 1, 1).getTimezoneOffset();
+  var t2 = new Date(y, 1 + 6, 1).getTimezoneOffset();
+  return (t1 != t2);
+}
+
+/*
+ * Don't apply DST near start of epoch unless absolutely necessary
+ */
+function IgnoreDaylightSaving(t)
+{
+  if ((0 <= t && t < msPerYear) && !DST_1970) {
+    return true;
+  }
+  if ((msPerYear <= t && t < 2*msPerYear) && !DST_1971) {
+    return true;
+  }
+  return false;
 }
 
 /*
@@ -74,14 +145,18 @@ function adjustResultArray(ResultArray, msMode)
   {
     // The hard-coded UTC milliseconds from Time 0 derives from a UTC date.
     // Shift to the right by the offset between UTC and the tester.
-    var t = ResultArray[TIME]  +  TZ_DIFF*msPerHour;
+    if (IgnoreDaylightSaving(ResultArray[TIME])) {
+      var t = ResultArray[TIME]  +  TZ_DIFF_RAW*msPerHour;
+    } else {
+      var t = ResultArray[TIME]  +  TZ_DIFF*msPerHour;
+    }
 
     // Use our date arithmetic functions to determine the local hour, day, etc.
     ResultArray[HOURS] = HourFromTime(t);
     ResultArray[DAY] = WeekDay(t);
     ResultArray[DATE] = DateFromTime(t);
     ResultArray[MONTH] = MonthFromTime(t);
-    ResultArray[YEAR] = YearFromTime(t); 
+    ResultArray[YEAR] = YearFromTime(t);
   }
   else
   {
@@ -295,7 +370,7 @@ function msFromTime( t ) {
   return ( (ms < 0 ) ? msPerSecond + ms : ms );
 }
 function LocalTZA() {
-  return ( TZ_DIFF * msPerHour );
+  return ( TZ_DIFF_RAW * msPerHour );
 }
 function UTC( t ) {
   return ( t - LocalTZA() - DaylightSavingTA(t - LocalTZA()) );
@@ -304,13 +379,27 @@ function LocalTime( t ) {
   return ( t + LocalTZA() + DaylightSavingTA(t) );
 }
 function DaylightSavingTA( t ) {
-  t = t - LocalTZA();
+  if (IgnoreDaylightSaving(t)) {
+    return 0;
+  }
 
-  var dst_start = GetDSTStart(t);
-  var dst_end   = GetDSTEnd(t);
+  if (DST_PERIOD > 0) {
+    // northern hemisphere
+    var dst_start = GetDSTStart(t);
+    var dst_end   = GetDSTEnd(t);
 
-  if ( t >= dst_start && t < dst_end )
-    return msPerHour;
+    if ( t >= dst_start && t < dst_end )
+      return msPerHour;
+  } else if (DST_PERIOD < 0) {
+    // southern hemisphere
+    var dst_start = GetDSTStart_Southern(t);
+    var dst_end   = GetDSTEnd_Southern(t);
+
+    if ( t >= dst_start && t < GetDSTEnd_Southern(t + msPerYear) )
+      return msPerHour;
+    if ( t < dst_end && t >= GetDSTEnd_Southern(t - msPerYear) )
+      return msPerHour;
+  }
 
   return 0;
 }
@@ -416,6 +505,21 @@ function GetOldDSTEnd( t )
   return (GetLastSundayInMonth(t, 9) + 2*msPerHour - LocalTZA());
 }
 
+/*
+ * Daylight saving time start/end date for 'Australia'
+ * (arbitrarily chosen as a representative for the southern hemisphere)
+ */
+
+function GetDSTStart_Southern( t )
+{
+  return (GetFirstSundayInMonth(t, 9) + 2*msPerHour - LocalTZA());
+}
+
+function GetDSTEnd_Southern( t )
+{
+  return (GetFirstSundayInMonth(t, 3) + 2*msPerHour - LocalTZA());
+}
+
 function MakeTime( hour, min, sec, ms ) {
   if ( isNaN( hour ) || isNaN( min ) || isNaN( sec ) || isNaN( ms ) ) {
     return Number.NaN;