Implement date library functions in C++.

src/date.js

Index: src/date.js
diff --git a/src/date.js b/src/date.js
index 2e5d6e22c40d8b5bdec0e671c081d3aabef8bbda..75edf6d32d17c364023c39cb319c937c1421286d 100644
--- a/src/date.js
+++ b/src/date.js
@@ -44,172 +44,6 @@ function ThrowDateTypeError() {
   throw new $TypeError('this is not a Date object.');
 }
 
-// ECMA 262 - 5.2
-function Modulo(value, remainder) {
-  var mod = value % remainder;
-  // All uses of this function for dates should produce a Smi.
-  return (mod >= 0 ? mod : mod + remainder) | 0;
-}
-
-
-function TimeWithinDay(time) {
-  return Modulo(time, msPerDay);
-}
-
-
-// ECMA 262 - 15.9.1.3
-function DaysInYear(year) {
-  if (year % 4 != 0) return 365;
-  if ((year % 100 == 0) && (year % 400 != 0)) return 365;
-  return 366;
-}
-
-
-function DayFromYear(year) {
-  return 365 * (year-1970)
-      + FLOOR((year-1969)/4)
-      - FLOOR((year-1901)/100)
-      + FLOOR((year-1601)/400);
-}
-
-
-function TimeFromYear(year) {
-  return msPerDay * DayFromYear(year);
-}
-
-
-function InLeapYear(time) {
-  return DaysInYear(YearFromTime(time)) - 365;  // Returns 1 or 0.
-}
-
-
-// ECMA 262 - 15.9.1.9
-function EquivalentYear(year) {
-  // Returns an equivalent year in the range [2008-2035] matching
-  // - leap year.
-  // - week day of first day.
-  var time = TimeFromYear(year);
-  var recent_year = (InLeapYear(time) == 0 ? 1967 : 1956) +
-      (WeekDay(time) * 12) % 28;
-  // Find the year in the range 2008..2037 that is equivalent mod 28.
-  // Add 3*28 to give a positive argument to the modulus operator.
-  return 2008 + (recent_year + 3*28 - 2008) % 28;
-}
-
-
-function EquivalentTime(t) {
-  // The issue here is that some library calls don't work right for dates
-  // that cannot be represented using a non-negative signed 32 bit integer
-  // (measured in whole seconds based on the 1970 epoch).
-  // We solve this by mapping the time to a year with same leap-year-ness
-  // and same starting day for the year.  The ECMAscript specification says
-  // we must do this, but for compatibility with other browsers, we use
-  // the actual year if it is in the range 1970..2037
-  if (t >= 0 && t <= 2.1e12) return t;
-
-  var day = MakeDay(EquivalentYear(YearFromTime(t)),
-                    MonthFromTime(t),
-                    DateFromTime(t));
-  return MakeDate(day, TimeWithinDay(t));
-}
-
-
-// local_time_offset is initialized when the DST_offset_cache is missed.
-// It must not be used until after a call to DaylightSavingsOffset().
-// In this way, only one check, for a DST cache miss, is needed.
-var local_time_offset;
-
-
-// Because computing the DST offset is an expensive operation,
-// we keep a cache of the last computed DST offset along with a time interval
-// where we know the cache is valid.
-// When the cache is valid, local_time_offset is also valid.
-var DST_offset_cache = {
-  // Cached DST offset.
-  offset: 0,
-  // Time interval where the cached offset is valid.
-  start: 0, end: -1,
-  // Size of next interval expansion.
-  increment: 0,
-  initial_increment: 19 * msPerDay
-};
-
-
-// NOTE: The implementation relies on the fact that no time zones have
-// more than one daylight savings offset change per 19 days.
-//
-// In Egypt in 2010 they decided to suspend DST during Ramadan. This
-// led to a short interval where DST is in effect from September 10 to
-// September 30.
-//
-// If this function is called with NaN it returns NaN.
-function DaylightSavingsOffset(t) {
-  // Load the cache object from the builtins object.
-  var cache = DST_offset_cache;
-
-  // Cache the start and the end in local variables for fast access.
-  var start = cache.start;
-  var end = cache.end;
-
-  if (start <= t) {
-    // If the time fits in the cached interval, return the cached offset.
-    if (t <= end) return cache.offset;
-
-    // If the cache misses, the local_time_offset may not be initialized.
-    if (IS_UNDEFINED(local_time_offset)) {
-      local_time_offset = %DateLocalTimeOffset();
-    }
-
-    // Compute a possible new interval end.
-    var new_end = end + cache.increment;
-
-    if (t <= new_end) {
-      var end_offset = %DateDaylightSavingsOffset(EquivalentTime(new_end));
-      if (cache.offset == end_offset) {
-        // If the offset at the end of the new interval still matches
-        // the offset in the cache, we grow the cached time interval
-        // and return the offset.
-        cache.end = new_end;
-        cache.increment = cache.initial_increment;
-        return end_offset;
-      } else {
-        var offset = %DateDaylightSavingsOffset(EquivalentTime(t));
-        if (offset == end_offset) {
-          // The offset at the given time is equal to the offset at the
-          // new end of the interval, so that means that we've just skipped
-          // the point in time where the DST offset change occurred. Updated
-          // the interval to reflect this and reset the increment.
-          cache.start = t;
-          cache.end = new_end;
-          cache.increment = cache.initial_increment;
-        } else {
-          // The interval contains a DST offset change and the given time is
-          // before it. Adjust the increment to avoid a linear search for
-          // the offset change point and change the end of the interval.
-          cache.increment /= 3;
-          cache.end = t;
-        }
-        // Update the offset in the cache and return it.
-        cache.offset = offset;
-        return offset;
-      }
-    }
-  }
-
-  // If the cache misses, the local_time_offset may not be initialized.
-  if (IS_UNDEFINED(local_time_offset)) {
-    local_time_offset = %DateLocalTimeOffset();
-  }
-  // Compute the DST offset for the time and shrink the cache interval
-  // to only contain the time. This allows fast repeated DST offset
-  // computations for the same time.
-  var offset = %DateDaylightSavingsOffset(EquivalentTime(t));
-  cache.offset = offset;
-  cache.start = cache.end = t;
-  cache.increment = cache.initial_increment;
-  return offset;
-}
-
 
 var timezone_cache_time = $NaN;
 var timezone_cache_timezone;
@@ -219,57 +53,18 @@ function LocalTimezone(t) {
   if (t == timezone_cache_time) {
     return timezone_cache_timezone;
   }
-  var timezone = %DateLocalTimezone(EquivalentTime(t));
+  var timezone = %DateLocalTimezone(t);
   timezone_cache_time = t;
   timezone_cache_timezone = timezone;
   return timezone;
 }
 
 
-function WeekDay(time) {
-  return Modulo(DAY(time) + 4, 7);
-}
-
-
-function LocalTime(time) {
-  if (NUMBER_IS_NAN(time)) return time;
-  // DaylightSavingsOffset called before local_time_offset used.
-  return time + DaylightSavingsOffset(time) + local_time_offset;
-}
-
-
-var ltcache = {
-  key: null,
-  val: null
-};
-
-function LocalTimeNoCheck(time) {
-  var ltc = ltcache;
-  if (%_ObjectEquals(time, ltc.key)) return ltc.val;
-
-  // Inline the DST offset cache checks for speed.
-  // The cache is hit, or DaylightSavingsOffset is called,
-  // before local_time_offset is used.
-  var cache = DST_offset_cache;
-  if (cache.start <= time && time <= cache.end) {
-    var dst_offset = cache.offset;
-  } else {
-    var dst_offset = DaylightSavingsOffset(time);
-  }
-  ltc.key = time;
-  return (ltc.val = time + local_time_offset + dst_offset);
-}
-
-
 function UTC(time) {
   if (NUMBER_IS_NAN(time)) return time;
   // local_time_offset is needed before the call to DaylightSavingsOffset,
   // so it may be uninitialized.
-  if (IS_UNDEFINED(local_time_offset)) {
-    local_time_offset = %DateLocalTimeOffset();
-  }
-  var tmp = time - local_time_offset;
-  return tmp - DaylightSavingsOffset(tmp);
+  return %DateToUTC(time);
 }
 
 
@@ -292,48 +87,6 @@ function TimeInYear(year) {
 }
 
 
-var ymd_from_time_cache = [1970, 0, 1];
-var ymd_from_time_cached_time = 0;
-
-function YearFromTime(t) {
-  if (t !== ymd_from_time_cached_time) {
-    if (!$isFinite(t)) {
-      return $NaN;
-    }
-
-    %DateYMDFromTime(t, ymd_from_time_cache);
-    ymd_from_time_cached_time = t;
-  }
-
-  return ymd_from_time_cache[0];
-}
-
-function MonthFromTime(t) {
-  if (t !== ymd_from_time_cached_time) {
-    if (!$isFinite(t)) {
-      return $NaN;
-    }
-    %DateYMDFromTime(t, ymd_from_time_cache);
-    ymd_from_time_cached_time = t;
-  }
-
-  return ymd_from_time_cache[1];
-}
-
-function DateFromTime(t) {
-  if (t !== ymd_from_time_cached_time) {
-    if (!$isFinite(t)) {
-      return $NaN;
-    }
-
-    %DateYMDFromTime(t, ymd_from_time_cache);
-    ymd_from_time_cached_time = t;
-  }
-
-  return ymd_from_time_cache[2];
-}
-
-
 // Compute number of days given a year, month, date.
 // Note that month and date can lie outside the normal range.
 //   For example:
@@ -384,9 +137,6 @@ function TimeClip(time) {
 var Date_cache = {
   // Cached time value.
   time: $NaN,
-  // Cached year when interpreting the time as a local time. Only
-  // valid when the time matches cached time.
-  year: $NaN,
   // String input for which the cached time is valid.
   string: null
 };
@@ -403,11 +153,10 @@ var Date_cache = {
   var value;
   if (argc == 0) {
     value = %DateCurrentTime();
-
+    SET_UTC_DATE_VALUE(this, value);
   } else if (argc == 1) {
     if (IS_NUMBER(year)) {
-      value = TimeClip(year);
-
+      value = year;
     } else if (IS_STRING(year)) {
       // Probe the Date cache. If we already have a time value for the
       // given time, we re-use that instead of parsing the string again.
@@ -418,7 +167,6 @@ var Date_cache = {
         value = DateParse(year);
         if (!NUMBER_IS_NAN(value)) {
           cache.time = value;
-          cache.year = YearFromTime(LocalTimeNoCheck(value));
           cache.string = year;
         }
       }
@@ -432,9 +180,9 @@ var Date_cache = {
       // which is the default for everything else than Date objects.
       // This makes us behave like KJS and SpiderMonkey.
       var time = ToPrimitive(year, NUMBER_HINT);
-      value = IS_STRING(time) ? DateParse(time) : TimeClip(ToNumber(time));
+      value = IS_STRING(time) ? DateParse(time) : ToNumber(time);
     }
-
+    SET_UTC_DATE_VALUE(this, value);
   } else {
     year = ToNumber(year);
     month = ToNumber(month);
@@ -448,40 +196,12 @@ var Date_cache = {
             TO_INTEGER(year) <= 99) ? 1900 + TO_INTEGER(year) : year;
     var day = MakeDay(year, month, date);
     var time = MakeTime(hours, minutes, seconds, ms);
-    value = TimeClip(UTC(MakeDate(day, time)));
+    value = MakeDate(day, time);
+    SET_LOCAL_DATE_VALUE(this, value);
   }
-  SET_DATE_VALUE(this, value);
 });
 
 
-function ResetDate(date, time) {
-  SET_DATE_VALUE(date, time);
-  // Cache aggressively in case of a reset - we will typically use most fields.
-  if (NUMBER_IS_NAN(time)) {
-    SET_DATE_LOCAL(date, time);
-    SET_DATE_YEAR(date, time);
-    SET_DATE_MONTH(date, time);
-    SET_DATE_DAY(date, time);
-    SET_DATE_HOUR(date, time);
-    SET_DATE_MIN(date, time);
-    SET_DATE_SEC(date, time);
-    SET_DATE_WEEKDAY(date, time);
-  } else {
-    var local = LocalTimeNoCheck(time);
-    SET_DATE_LOCAL(date, local_time_offset);
-    SET_DATE_YEAR(date, YearFromTime(local));
-    SET_DATE_MONTH(date, MonthFromTime(local));
-    SET_DATE_DAY(date, DateFromTime(local));
-    SET_DATE_HOUR(date, HOUR_FROM_TIME(local));
-    SET_DATE_MIN(date, MIN_FROM_TIME(local));
-    SET_DATE_SEC(date, SEC_FROM_TIME(local));
-    SET_DATE_WEEKDAY(date, WeekDay(local));
-  }
-
-  return time;
-}
-
-
 %FunctionSetPrototype($Date, new $Date($NaN));
 
 
@@ -495,11 +215,11 @@ function TwoDigitString(value) {
 }
 
 
-function DateString(time) {
-  return WeekDays[WeekDay(time)] + ' '
-      + Months[MonthFromTime(time)] + ' '
-      + TwoDigitString(DateFromTime(time)) + ' '
-      + YearFromTime(time);
+function DateString(date) {
+  return WeekDays[LOCAL_WEEKDAY(date)] + ' '
+      + Months[LOCAL_MONTH(date)] + ' '
+      + TwoDigitString(LOCAL_DAY(date)) + ' '
+      + LOCAL_YEAR(date);
 }
 
 
@@ -509,38 +229,32 @@ var LongMonths = ['January', 'February', 'March', 'April', 'May', 'June',
     'July', 'August', 'September', 'October', 'November', 'December'];
 
 
-function LongDateString(time) {
-  return LongWeekDays[WeekDay(time)] + ', '
-      + LongMonths[MonthFromTime(time)] + ' '
-      + TwoDigitString(DateFromTime(time)) + ', '
-      + YearFromTime(time);
+function LongDateString(date) {
+  return LongWeekDays[LOCAL_WEEKDAY(date)] + ', '
+      + LongMonths[LOCAL_MONTH(date)] + ' '
+      + TwoDigitString(LOCAL_DAY(date)) + ', '
+      + LOCAL_YEAR(date);
 }
 
 
-function TimeString(time) {
-  return TwoDigitString(HOUR_FROM_TIME(time)) + ':'
-      + TwoDigitString(MIN_FROM_TIME(time)) + ':'
-      + TwoDigitString(SEC_FROM_TIME(time));
+function TimeString(date) {
+  return TwoDigitString(LOCAL_HOUR(date)) + ':'
+      + TwoDigitString(LOCAL_MIN(date)) + ':'
+      + TwoDigitString(LOCAL_SEC(date));
 }
 
 
-function LocalTimezoneString(time) {
-  var old_timezone = timezone_cache_timezone;
-  var timezone = LocalTimezone(time);
-  if (old_timezone && timezone != old_timezone) {
-    // If the timezone string has changed from the one that we cached,
-    // the local time offset may now be wrong. So we need to update it
-    // and try again.
-    local_time_offset = %DateLocalTimeOffset();
-    // We also need to invalidate the DST cache as the new timezone may have
-    // different DST times.
-    var dst_cache = DST_offset_cache;
-    dst_cache.start = 0;
-    dst_cache.end = -1;
-  }
+function TimeStringUTC(date) {
+  return TwoDigitString(UTC_HOUR(date)) + ':'
+      + TwoDigitString(UTC_MIN(date)) + ':'
+      + TwoDigitString(UTC_SEC(date));
+}
+
 
-  var timezoneOffset =
-      (DaylightSavingsOffset(time) + local_time_offset) / msPerMinute;
+function LocalTimezoneString(date) {
+  var timezone = LocalTimezone(UTC_DATE_VALUE(date));
+
+  var timezoneOffset = -TIMEZONE_OFFSET(date);
   var sign = (timezoneOffset >= 0) ? 1 : -1;
   var hours = FLOOR((sign * timezoneOffset)/60);
   var min   = FLOOR((sign * timezoneOffset)%60);
@@ -550,8 +264,8 @@ function LocalTimezoneString(time) {
 }
 
 
-function DatePrintString(time) {
-  return DateString(time) + ' ' + TimeString(time);
+function DatePrintString(date) {
+  return DateString(date) + ' ' + TimeString(date);
 }
 
 // -------------------------------------------------------------------
@@ -604,27 +318,30 @@ function DateNow() {
 
 // ECMA 262 - 15.9.5.2
 function DateToString() {
-  var t = DATE_VALUE(this);
+  CHECK_DATE(this);
+  var t = UTC_DATE_VALUE(this)
   if (NUMBER_IS_NAN(t)) return kInvalidDate;
-  var time_zone_string = LocalTimezoneString(t);  // May update local offset.
-  return DatePrintString(LocalTimeNoCheck(t)) + time_zone_string;
+  var time_zone_string = LocalTimezoneString(this)
+  return DatePrintString(this) + time_zone_string;
 }
 
 
 // ECMA 262 - 15.9.5.3
 function DateToDateString() {
-  var t = DATE_VALUE(this);
+  CHECK_DATE(this);
+  var t = UTC_DATE_VALUE(this);
   if (NUMBER_IS_NAN(t)) return kInvalidDate;
-  return DateString(LocalTimeNoCheck(t));
+  return DateString(this);
 }
 
 
 // ECMA 262 - 15.9.5.4
 function DateToTimeString() {
-  var t = DATE_VALUE(this);
+  CHECK_DATE(this);
+  var t = UTC_DATE_VALUE(this);
   if (NUMBER_IS_NAN(t)) return kInvalidDate;
-  var time_zone_string = LocalTimezoneString(t);  // May update local offset.
-  return TimeString(LocalTimeNoCheck(t)) + time_zone_string;
+  var time_zone_string = LocalTimezoneString(this);
+  return TimeString(this) + time_zone_string;
 }
 
 
@@ -636,372 +353,388 @@ function DateToLocaleString() {
 
 // ECMA 262 - 15.9.5.6
 function DateToLocaleDateString() {
-  var t = DATE_VALUE(this);
+  CHECK_DATE(this);
+  var t = UTC_DATE_VALUE(this);
   if (NUMBER_IS_NAN(t)) return kInvalidDate;
-  return LongDateString(LocalTimeNoCheck(t));
+  return LongDateString(this);
 }
 
 
 // ECMA 262 - 15.9.5.7
 function DateToLocaleTimeString() {
-  var t = DATE_VALUE(this);
+  CHECK_DATE(this);
+  var t = UTC_DATE_VALUE(this);
   if (NUMBER_IS_NAN(t)) return kInvalidDate;
-  var lt = LocalTimeNoCheck(t);
-  return TimeString(lt);
+  return TimeString(this);
 }
 
 
 // ECMA 262 - 15.9.5.8
 function DateValueOf() {
-  return DATE_VALUE(this);
+  CHECK_DATE(this);
+  return UTC_DATE_VALUE(this);
 }
 
 
 // ECMA 262 - 15.9.5.9
 function DateGetTime() {
-  return DATE_VALUE(this);
+  CHECK_DATE(this);
+  return UTC_DATE_VALUE(this);
 }
 
 
 // ECMA 262 - 15.9.5.10
 function DateGetFullYear() {
-  var t = DATE_YEAR(this);
-  if (!IS_UNDEFINED(t) && DATE_LOCAL(this) === local_time_offset) return t;
-  t = DATE_VALUE_UNCHECKED(this);
-  var cache = Date_cache;
-  if (cache.time === t) return cache.year;
-  t = LocalTimeNoCheck(t);
-  if (!NUMBER_IS_NAN(t)) t = YearFromTime(t);
-  return t;
+  CHECK_DATE(this);
+  return LOCAL_YEAR(this);
 }
 
 
 // ECMA 262 - 15.9.5.11
 function DateGetUTCFullYear() {
-  var t = DATE_VALUE(this);
-  if (NUMBER_IS_NAN(t)) return t;
-  return YearFromTime(t);
+  CHECK_DATE(this);
+  return UTC_YEAR(this);
 }
 
 
 // ECMA 262 - 15.9.5.12
 function DateGetMonth() {
-  var t = DATE_MONTH(this);
-  if (!IS_UNDEFINED(t) && DATE_LOCAL(this) === local_time_offset) return t;
-  ResetDate(this, DATE_VALUE_UNCHECKED(this));
-  return DATE_MONTH(this);
+  CHECK_DATE(this);
+  return LOCAL_MONTH(this);
 }
 
 
 // ECMA 262 - 15.9.5.13
 function DateGetUTCMonth() {
-  var t = DATE_VALUE(this);
-  if (NUMBER_IS_NAN(t)) return t;
-  return MonthFromTime(t);
+  CHECK_DATE(this);
+  return UTC_MONTH(this);
 }
 
 
 // ECMA 262 - 15.9.5.14
 function DateGetDate() {
-  var t = DATE_DAY(this);
-  if (!IS_UNDEFINED(t) && DATE_LOCAL(this) === local_time_offset) return t;
-  ResetDate(this, DATE_VALUE_UNCHECKED(this));
-  return DATE_DAY(this);
+  CHECK_DATE(this);
+  return LOCAL_DAY(this);
 }
 
 
 // ECMA 262 - 15.9.5.15
 function DateGetUTCDate() {
-  var t = DATE_VALUE(this);
-  return NAN_OR_DATE_FROM_TIME(t);
+  CHECK_DATE(this);
+  return UTC_DAY(this);
 }
 
 
 // ECMA 262 - 15.9.5.16
 function DateGetDay() {
-  var t = DATE_WEEKDAY(this);
-  if (!IS_UNDEFINED(t) && DATE_LOCAL(this) === local_time_offset) return t;
-  ResetDate(this, DATE_VALUE_UNCHECKED(this));
-  return DATE_WEEKDAY(this);
+  CHECK_DATE(this);
+  return LOCAL_WEEKDAY(this);
 }
 
 
 // ECMA 262 - 15.9.5.17
 function DateGetUTCDay() {
-  var t = DATE_VALUE(this);
-  if (NUMBER_IS_NAN(t)) return t;
-  return WeekDay(t);
+  CHECK_DATE(this);
+  return UTC_WEEKDAY(this);
 }
 
 
 // ECMA 262 - 15.9.5.18
 function DateGetHours() {
-  var t = DATE_HOUR(this);
-  if (!IS_UNDEFINED(t) && DATE_LOCAL(this) === local_time_offset) return t;
-  ResetDate(this, DATE_VALUE_UNCHECKED(this));
-  return DATE_HOUR(this);
+  CHECK_DATE(this);
+  return LOCAL_HOUR(this);
 }
 
 
 // ECMA 262 - 15.9.5.19
 function DateGetUTCHours() {
-  var t = DATE_VALUE(this);
-  if (NUMBER_IS_NAN(t)) return t;
-  return HOUR_FROM_TIME(t);
+  CHECK_DATE(this);
+  return UTC_HOUR(this);
 }
 
 
 // ECMA 262 - 15.9.5.20
 function DateGetMinutes() {
-  var t = DATE_MIN(this);
-  if (!IS_UNDEFINED(t) && DATE_LOCAL(this) === local_time_offset) return t;
-  ResetDate(this, DATE_VALUE_UNCHECKED(this));
-  return DATE_MIN(this);
+  CHECK_DATE(this);
+  return LOCAL_MIN(this);
 }
 
 
 // ECMA 262 - 15.9.5.21
 function DateGetUTCMinutes() {
-  var t = DATE_VALUE(this);
-  return NAN_OR_MIN_FROM_TIME(t);
+  CHECK_DATE(this);
+  return UTC_MIN(this);
 }
 
 
 // ECMA 262 - 15.9.5.22
 function DateGetSeconds() {
-  var t = DATE_SEC(this);
-  if (!IS_UNDEFINED(t) && DATE_LOCAL(this) === local_time_offset) return t;
-  ResetDate(this, DATE_VALUE_UNCHECKED(this));
-  return DATE_SEC(this);
+  CHECK_DATE(this);
+  return LOCAL_SEC(this);
 }
 
 
 // ECMA 262 - 15.9.5.23
 function DateGetUTCSeconds() {
-  var t = DATE_VALUE(this);
-  return NAN_OR_SEC_FROM_TIME(t);
+  CHECK_DATE(this);
+  return UTC_SEC(this)
 }
 
 
 // ECMA 262 - 15.9.5.24
 function DateGetMilliseconds() {
-  var t = DATE_VALUE(this);
-  if (NUMBER_IS_NAN(t)) return t;
-  return MS_FROM_TIME(LocalTimeNoCheck(t));
+  CHECK_DATE(this);
+  return LOCAL_MS(this);
 }
 
 
 // ECMA 262 - 15.9.5.25
 function DateGetUTCMilliseconds() {
-  var t = DATE_VALUE(this);
-  return NAN_OR_MS_FROM_TIME(t);
+  CHECK_DATE(this);
+  return UTC_MS(this);
 }
 
 
 // ECMA 262 - 15.9.5.26
 function DateGetTimezoneOffset() {
-  var t = DATE_VALUE(this);
-  if (NUMBER_IS_NAN(t)) return t;
-  return (t - LocalTimeNoCheck(t)) / msPerMinute;
+  CHECK_DATE(this);
+  return TIMEZONE_OFFSET(this);
 }
 
 
 // ECMA 262 - 15.9.5.27
 function DateSetTime(ms) {
-  if (!IS_DATE(this)) ThrowDateTypeError();
-  return ResetDate(this, TimeClip(ToNumber(ms)));
+  CHECK_DATE(this);
+  SET_UTC_DATE_VALUE(this, ToNumber(ms));
+  return UTC_DATE_VALUE(this);
 }
 
 
 // ECMA 262 - 15.9.5.28
 function DateSetMilliseconds(ms) {
-  var t = LocalTime(DATE_VALUE(this));
+  CHECK_DATE(this);
+  var t = LOCAL_DATE_VALUE(this);
   ms = ToNumber(ms);
-  var time = MakeTime(HOUR_FROM_TIME(t),
-                      MIN_FROM_TIME(t),
-                      SEC_FROM_TIME(t),
-                      ms);
-  return ResetDate(this, TimeClip(UTC(MakeDate(DAY(t), time))));
+  var time = MakeTime(LOCAL_HOUR(this), LOCAL_MIN(this), LOCAL_SEC(this), ms);
+  SET_LOCAL_DATE_VALUE(this, MakeDate(LOCAL_DAYS(this), time));
+  return this;
 }
 
 
 // ECMA 262 - 15.9.5.29
 function DateSetUTCMilliseconds(ms) {
-  var t = DATE_VALUE(this);
+  CHECK_DATE(this);
+  var t = UTC_DATE_VALUE(this);
   ms = ToNumber(ms);
-  var time = MakeTime(HOUR_FROM_TIME(t),
-                      MIN_FROM_TIME(t),
-                      SEC_FROM_TIME(t),
+  var time = MakeTime(UTC_HOUR(this),
+                      UTC_MIN(this),
+                      UTC_SEC(this),
                       ms);
-  return ResetDate(this, TimeClip(MakeDate(DAY(t), time)));
+  return SET_UTC_DATE_VALUE(this, MakeDate(UTC_DAYS(this), time));
 }
 
 
 // ECMA 262 - 15.9.5.30
 function DateSetSeconds(sec, ms) {
-  var t = LocalTime(DATE_VALUE(this));
+  CHECK_DATE(this);
+  var t = LOCAL_DATE_VALUE(this);
   sec = ToNumber(sec);
-  ms = %_ArgumentsLength() < 2 ? NAN_OR_MS_FROM_TIME(t) : ToNumber(ms);
-  var time = MakeTime(HOUR_FROM_TIME(t), MIN_FROM_TIME(t), sec, ms);
-  return ResetDate(this, TimeClip(UTC(MakeDate(DAY(t), time))));
+  ms = %_ArgumentsLength() < 2 ? LOCAL_MS(this) : ToNumber(ms);
+  var time = MakeTime(LOCAL_HOUR(this), LOCAL_MIN(this), sec, ms);
+  return SET_LOCAL_DATE_VALUE(this, MakeDate(LOCAL_DAYS(this), time));
 }
 
 
 // ECMA 262 - 15.9.5.31
 function DateSetUTCSeconds(sec, ms) {
-  var t = DATE_VALUE(this);
+  CHECK_DATE(this);
+  var t = UTC_DATE_VALUE(this);
   sec = ToNumber(sec);
-  ms = %_ArgumentsLength() < 2 ? NAN_OR_MS_FROM_TIME(t) : ToNumber(ms);
-  var time = MakeTime(HOUR_FROM_TIME(t), MIN_FROM_TIME(t), sec, ms);
-  return ResetDate(this, TimeClip(MakeDate(DAY(t), time)));
+  ms = %_ArgumentsLength() < 2 ? UTC_MS(this) : ToNumber(ms);
+  var time = MakeTime(UTC_HOUR(this), UTC_MIN(this), sec, ms);
+  return SET_UTC_DATE_VALUE(this, MakeDate(UTC_DAYS(this), time));
 }
 
 
 // ECMA 262 - 15.9.5.33
 function DateSetMinutes(min, sec, ms) {
-  var t = LocalTime(DATE_VALUE(this));
+  CHECK_DATE(this);
+  var t = LOCAL_DATE_VALUE(this);
   min = ToNumber(min);
   var argc = %_ArgumentsLength();
-  sec = argc < 2 ? NAN_OR_SEC_FROM_TIME(t) : ToNumber(sec);
-  ms = argc < 3 ? NAN_OR_MS_FROM_TIME(t) : ToNumber(ms);
-  var time = MakeTime(HOUR_FROM_TIME(t), min, sec, ms);
-  return ResetDate(this, TimeClip(UTC(MakeDate(DAY(t), time))));
+  sec = argc < 2 ? LOCAL_SEC(this) : ToNumber(sec);
+  ms = argc < 3 ? LOCAL_MS(this) : ToNumber(ms);
+  var time = MakeTime(LOCAL_HOUR(this), min, sec, ms);
+  return SET_LOCAL_DATE_VALUE(this, MakeDate(LOCAL_DAYS(this), time));
 }
 
 
 // ECMA 262 - 15.9.5.34
 function DateSetUTCMinutes(min, sec, ms) {
-  var t = DATE_VALUE(this);
+  CHECK_DATE(this);
+  var t = UTC_DATE_VALUE(this);
   min = ToNumber(min);
   var argc = %_ArgumentsLength();
-  sec = argc < 2 ? NAN_OR_SEC_FROM_TIME(t) : ToNumber(sec);
-  ms = argc < 3 ? NAN_OR_MS_FROM_TIME(t) : ToNumber(ms);
-  var time = MakeTime(HOUR_FROM_TIME(t), min, sec, ms);
-  return ResetDate(this, TimeClip(MakeDate(DAY(t), time)));
+  sec = argc < 2 ? UTC_SEC(this) : ToNumber(sec);
+  ms = argc < 3 ? UTC_MS(this) : ToNumber(ms);
+  var time = MakeTime(UTC_HOUR(this), min, sec, ms);
+  return SET_UTC_DATE_VALUE(this, MakeDate(UTC_DAYS(this), time));
 }
 
 
 // ECMA 262 - 15.9.5.35
 function DateSetHours(hour, min, sec, ms) {
-  var t = LocalTime(DATE_VALUE(this));
+  CHECK_DATE(this);
+  var t = LOCAL_DATE_VALUE(this);
   hour = ToNumber(hour);
   var argc = %_ArgumentsLength();
-  min = argc < 2 ? NAN_OR_MIN_FROM_TIME(t) : ToNumber(min);
-  sec = argc < 3 ? NAN_OR_SEC_FROM_TIME(t) : ToNumber(sec);
-  ms = argc < 4 ? NAN_OR_MS_FROM_TIME(t) : ToNumber(ms);
+  min = argc < 2 ? LOCAL_MIN(this) : ToNumber(min);
+  sec = argc < 3 ? LOCAL_SEC(this) : ToNumber(sec);
+  ms = argc < 4 ? LOCAL_MS(this) : ToNumber(ms);
   var time = MakeTime(hour, min, sec, ms);
-  return ResetDate(this, TimeClip(UTC(MakeDate(DAY(t), time))));
+  return SET_LOCAL_DATE_VALUE(this, MakeDate(LOCAL_DAYS(this), time));
 }
 
 
 // ECMA 262 - 15.9.5.34
 function DateSetUTCHours(hour, min, sec, ms) {
-  var t = DATE_VALUE(this);
+  CHECK_DATE(this);
+  var t = UTC_DATE_VALUE(this);
   hour = ToNumber(hour);
   var argc = %_ArgumentsLength();
-  min = argc < 2 ? NAN_OR_MIN_FROM_TIME(t) : ToNumber(min);
-  sec = argc < 3 ? NAN_OR_SEC_FROM_TIME(t) : ToNumber(sec);
-  ms = argc < 4 ? NAN_OR_MS_FROM_TIME(t) : ToNumber(ms);
+  min = argc < 2 ? UTC_MIN(this) : ToNumber(min);
+  sec = argc < 3 ? UTC_SEC(this) : ToNumber(sec);
+  ms = argc < 4 ? UTC_MS(this) : ToNumber(ms);
   var time = MakeTime(hour, min, sec, ms);
-  return ResetDate(this, TimeClip(MakeDate(DAY(t), time)));
+  return SET_UTC_DATE_VALUE(this, MakeDate(UTC_DAYS(this), time));
 }
 
 
 // ECMA 262 - 15.9.5.36
 function DateSetDate(date) {
-  var t = LocalTime(DATE_VALUE(this));
+  CHECK_DATE(this);
+  var t = LOCAL_DATE_VALUE(this);
   date = ToNumber(date);
-  var day = MakeDay(YearFromTime(t), MonthFromTime(t), date);
-  return ResetDate(this, TimeClip(UTC(MakeDate(day, TimeWithinDay(t)))));
+  var day = MakeDay(LOCAL_YEAR(this), LOCAL_MONTH(this), date);
+  return SET_LOCAL_DATE_VALUE(this, MakeDate(day, LOCAL_TIME_IN_DAY(this)));
 }
 
 
 // ECMA 262 - 15.9.5.37
 function DateSetUTCDate(date) {
-  var t = DATE_VALUE(this);
+  CHECK_DATE(this);
+  var t = UTC_DATE_VALUE(this);
   date = ToNumber(date);
-  var day = MakeDay(YearFromTime(t), MonthFromTime(t), date);
-  return ResetDate(this, TimeClip(MakeDate(day, TimeWithinDay(t))));
+  var day = MakeDay(UTC_YEAR(this), UTC_MONTH(this), date);
+  return SET_UTC_DATE_VALUE(this, MakeDate(day, UTC_TIME_IN_DAY(this)));
 }
 
 
 // ECMA 262 - 15.9.5.38
 function DateSetMonth(month, date) {
-  var t = LocalTime(DATE_VALUE(this));
+  CHECK_DATE(this);
+  var t = LOCAL_DATE_VALUE(this);
   month = ToNumber(month);
-  date = %_ArgumentsLength() < 2 ? NAN_OR_DATE_FROM_TIME(t) : ToNumber(date);
-  var day = MakeDay(YearFromTime(t), month, date);
-  return ResetDate(this, TimeClip(UTC(MakeDate(day, TimeWithinDay(t)))));
+  date = %_ArgumentsLength() < 2 ? LOCAL_DAY(this) : ToNumber(date);
+  var day = MakeDay(LOCAL_YEAR(this), month, date);
+  return SET_LOCAL_DATE_VALUE(this, MakeDate(day, LOCAL_TIME_IN_DAY(this)));
 }
 
 
 // ECMA 262 - 15.9.5.39
 function DateSetUTCMonth(month, date) {
-  var t = DATE_VALUE(this);
+  CHECK_DATE(this);
+  var t = UTC_DATE_VALUE(this);
   month = ToNumber(month);
-  date = %_ArgumentsLength() < 2 ? NAN_OR_DATE_FROM_TIME(t) : ToNumber(date);
-  var day = MakeDay(YearFromTime(t), month, date);
-  return ResetDate(this, TimeClip(MakeDate(day, TimeWithinDay(t))));
+  date = %_ArgumentsLength() < 2 ? UTC_DAY(this) : ToNumber(date);
+  var day = MakeDay(UTC_YEAR(this), month, date);
+  return SET_UTC_DATE_VALUE(this, MakeDate(day, UTC_TIME_IN_DAY(this)));
 }
 
 
 // ECMA 262 - 15.9.5.40
 function DateSetFullYear(year, month, date) {
-  var t = DATE_VALUE(this);
-  t = NUMBER_IS_NAN(t) ? 0 : LocalTimeNoCheck(t);
+  CHECK_DATE(this);
+  var t = LOCAL_DATE_VALUE(this);
   year = ToNumber(year);
   var argc = %_ArgumentsLength();
-  month = argc < 2 ? MonthFromTime(t) : ToNumber(month);
-  date = argc < 3 ? DateFromTime(t) : ToNumber(date);
+  var time ;
+  if (NUMBER_IS_NAN(t)) {
+    month = argc < 2 ? 0 : ToNumber(month);
+    date = argc < 3 ? 1 : ToNumber(date);
+    time = 0;
+  } else {
+    month = argc < 2 ? LOCAL_MONTH(this) : ToNumber(month);
+    date = argc < 3 ? LOCAL_DAY(this) : ToNumber(date);
+    time = LOCAL_TIME_IN_DAY(this);
+  }
   var day = MakeDay(year, month, date);
-  return ResetDate(this, TimeClip(UTC(MakeDate(day, TimeWithinDay(t)))));
+  return SET_LOCAL_DATE_VALUE(this, MakeDate(day, time));
 }
 
 
 // ECMA 262 - 15.9.5.41
 function DateSetUTCFullYear(year, month, date) {
-  var t = DATE_VALUE(this);
-  if (NUMBER_IS_NAN(t)) t = 0;
-  var argc = %_ArgumentsLength();
+  CHECK_DATE(this);
+  var t = UTC_DATE_VALUE(this);
   year = ToNumber(year);
-  month = argc < 2 ? MonthFromTime(t) : ToNumber(month);
-  date = argc < 3 ? DateFromTime(t) : ToNumber(date);
+  var argc = %_ArgumentsLength();
+  var time ;
+  if (NUMBER_IS_NAN(t)) {
+    month = argc < 2 ? 0 : ToNumber(month);
+    date = argc < 3 ? 1 : ToNumber(date);
+    time = 0;
+  } else {
+    month = argc < 2 ? UTC_MONTH(this) : ToNumber(month);
+    date = argc < 3 ? UTC_DAY(this) : ToNumber(date);
+    time = UTC_TIME_IN_DAY(this);
+  }
   var day = MakeDay(year, month, date);
-  return ResetDate(this, TimeClip(MakeDate(day, TimeWithinDay(t))));
+  return SET_UTC_DATE_VALUE(this, MakeDate(day, time));
 }
 
 
 // ECMA 262 - 15.9.5.42
 function DateToUTCString() {
-  var t = DATE_VALUE(this);
+  CHECK_DATE(this);
+  var t = UTC_DATE_VALUE(this);
   if (NUMBER_IS_NAN(t)) return kInvalidDate;
   // Return UTC string of the form: Sat, 31 Jan 1970 23:00:00 GMT
-  return WeekDays[WeekDay(t)] + ', '
-      + TwoDigitString(DateFromTime(t)) + ' '
-      + Months[MonthFromTime(t)] + ' '
-      + YearFromTime(t) + ' '
-      + TimeString(t) + ' GMT';
+  return WeekDays[UTC_WEEKDAY(this)] + ', '
+      + TwoDigitString(UTC_DAY(this)) + ' '
+      + Months[UTC_MONTH(this)] + ' '
+      + UTC_YEAR(this) + ' '
+      + TimeStringUTC(this) + ' GMT';
 }
 
 
 // ECMA 262 - B.2.4
 function DateGetYear() {
-  var t = DATE_VALUE(this);
-  if (NUMBER_IS_NAN(t)) return $NaN;
-  return YearFromTime(LocalTimeNoCheck(t)) - 1900;
+  CHECK_DATE(this);
+  return LOCAL_YEAR(this) - 1900;
 }
 
 
 // ECMA 262 - B.2.5
 function DateSetYear(year) {
-  var t = LocalTime(DATE_VALUE(this));
-  if (NUMBER_IS_NAN(t)) t = 0;
+  CHECK_DATE(this);
   year = ToNumber(year);
-  if (NUMBER_IS_NAN(year)) return ResetDate(this, $NaN);
+  if (NUMBER_IS_NAN(year)) return SET_UTC_DATE_VALUE(this, $NaN);
   year = (0 <= TO_INTEGER(year) && TO_INTEGER(year) <= 99)
       ? 1900 + TO_INTEGER(year) : year;
-  var day = MakeDay(year, MonthFromTime(t), DateFromTime(t));
-  return ResetDate(this, TimeClip(UTC(MakeDate(day, TimeWithinDay(t)))));
+  var t = LOCAL_DATE_VALUE(this);
+  var month, date, time;
+  if (NUMBER_IS_NAN(t))  {
+    month = 0;
+    date = 1;
+    time = 0;
+  } else {
+    month = LOCAL_MONTH(this);
+    date = LOCAL_DAY(this);
+    time = LOCAL_TIME_IN_DAY(this);
+  }
+  var day = MakeDay(year, month, date);
+  return SET_LOCAL_DATE_VALUE(this, MakeDate(day, time));
 }
 
 
@@ -1025,7 +758,8 @@ function PadInt(n, digits) {
 
 // ECMA 262 - 15.9.5.43
 function DateToISOString() {
-  var t = DATE_VALUE(this);
+  CHECK_DATE(this);
+  var t = UTC_DATE_VALUE(this);
   if (NUMBER_IS_NAN(t)) throw MakeRangeError("invalid_time_value", []);
   var year = this.getUTCFullYear();
   var year_string;
@@ -1060,34 +794,13 @@ function DateToJSON(key) {
 
 
 function ResetDateCache() {
-
-  // Reset the local_time_offset:
-  local_time_offset = %DateLocalTimeOffset();
-
-  // Reset the DST offset cache:
-  var cache = DST_offset_cache;
-  cache.offset = 0;
-  cache.start = 0;
-  cache.end = -1;
-  cache.increment = 0;
-  cache.initial_increment = 19 * msPerDay;
-
   // Reset the timezone cache:
   timezone_cache_time = $NaN;
   timezone_cache_timezone = undefined;
 
-  // Reset the ltcache:
-  ltcache.key = null;
-  ltcache.val = null;
-
-  // Reset the ymd_from_time_cache:
-  ymd_from_time_cache = [$NaN, $NaN, $NaN];
-  ymd_from_time_cached_time = $NaN;
-
   // Reset the date cache:
   cache = Date_cache;
   cache.time = $NaN;
-  cache.year = $NaN;
   cache.string = null;
 }