src/date.js

// Copyright 2006-2008 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
//       notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
//       copyright notice, this list of conditions and the following
//       disclaimer in the documentation and/or other materials provided
//       with the distribution.
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//       contributors may be used to endorse or promote products derived
//       from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.


// This file relies on the fact that the following declarations have been made
// in v8natives.js:
// const $isFinite = GlobalIsFinite;

// -------------------------------------------------------------------

// This file contains date support implemented in JavaScript.


// Keep reference to original values of some global properties.  This
// has the added benefit that the code in this file is isolated from
// changes to these properties.
const $Date = global.Date;

// Helper function to throw error.
function ThrowDateTypeError() {
  throw new $TypeError('this is not a Date object.');
}

// ECMA 262 - 5.2
function Modulo(value, remainder) {
  var mod = value % remainder;
  // Guard against returning -0.
  if (mod == 0) return 0;
  return mod >= 0 ? mod : mod + remainder;
}


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;

function LocalTimezone(t) {
  if (NUMBER_IS_NAN(t)) return "";
  if (t == timezone_cache_time) {
    return timezone_cache_timezone;
  }
  var timezone = %DateLocalTimezone(EquivalentTime(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);
}


// ECMA 262 - 15.9.1.11
function MakeTime(hour, min, sec, ms) {
  if (!$isFinite(hour)) return $NaN;
  if (!$isFinite(min)) return $NaN;
  if (!$isFinite(sec)) return $NaN;
  if (!$isFinite(ms)) return $NaN;
  return TO_INTEGER(hour) * msPerHour
      + TO_INTEGER(min) * msPerMinute
      + TO_INTEGER(sec) * msPerSecond
      + TO_INTEGER(ms);
}


// ECMA 262 - 15.9.1.12
function TimeInYear(year) {
  return DaysInYear(year) * msPerDay;
}


var ymd_from_time_cache = [$NaN, $NaN, $NaN];
var ymd_from_time_cached_time = $NaN;

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:
//     MakeDay(2007, -4, 20) --> MakeDay(2006, 8, 20)
//     MakeDay(2007, -33, 1) --> MakeDay(2004, 3, 1)
//     MakeDay(2007, 14, -50) --> MakeDay(2007, 8, 11)
function MakeDay(year, month, date) {
  if (!$isFinite(year) || !$isFinite(month) || !$isFinite(date)) return $NaN;

  // Convert to integer and map -0 to 0.
  year = TO_INTEGER_MAP_MINUS_ZERO(year);
  month = TO_INTEGER_MAP_MINUS_ZERO(month);
  date = TO_INTEGER_MAP_MINUS_ZERO(date);

  if (year < kMinYear || year > kMaxYear ||
      month < kMinMonth || month > kMaxMonth ||
      date < kMinDate || date > kMaxDate) {
    return $NaN;
  }

  // Now we rely on year, month and date being SMIs.
  return %DateMakeDay(year, month, date);
}


// ECMA 262 - 15.9.1.13
function MakeDate(day, time) {
  var time = day * msPerDay + time;
  // Some of our runtime funtions for computing UTC(time) rely on
  // times not being significantly larger than MAX_TIME_MS. If there
  // is no way that the time can be within range even after UTC
  // conversion we return NaN immediately instead of relying on
  // TimeClip to do it.
  if ($abs(time) > MAX_TIME_BEFORE_UTC) return $NaN;
  return time;
}


// ECMA 262 - 15.9.1.14
function TimeClip(time) {
  if (!$isFinite(time)) return $NaN;
  if ($abs(time) > MAX_TIME_MS) return $NaN;
  return TO_INTEGER(time);
}


// The Date cache is used to limit the cost of parsing the same Date
// strings over and over again.
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
};


%SetCode($Date, function(year, month, date, hours, minutes, seconds, ms) {
  if (!%_IsConstructCall()) {
    // ECMA 262 - 15.9.2
    return (new $Date()).toString();
  }

  // ECMA 262 - 15.9.3
  var argc = %_ArgumentsLength();
  var value;
  if (argc == 0) {
    value = %DateCurrentTime();

  } else if (argc == 1) {
    if (IS_NUMBER(year)) {
      value = TimeClip(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.
      var cache = Date_cache;
      if (cache.string === year) {
        value = cache.time;
      } else {
        value = DateParse(year);
        if (!NUMBER_IS_NAN(value)) {
          cache.time = value;
          cache.year = YearFromTime(LocalTimeNoCheck(value));
          cache.string = year;
        }
      }

    } else {
      // According to ECMA 262, no hint should be given for this
      // conversion. However, ToPrimitive defaults to STRING_HINT for
      // Date objects which will lose precision when the Date
      // constructor is called with another Date object as its
      // argument. We therefore use NUMBER_HINT for the conversion,
      // 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));
    }

  } else {
    year = ToNumber(year);
    month = ToNumber(month);
    date = argc > 2 ? ToNumber(date) : 1;
    hours = argc > 3 ? ToNumber(hours) : 0;
    minutes = argc > 4 ? ToNumber(minutes) : 0;
    seconds = argc > 5 ? ToNumber(seconds) : 0;
    ms = argc > 6 ? ToNumber(ms) : 0;
    year = (!NUMBER_IS_NAN(year) && 0 <= TO_INTEGER(year) && 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)));
  }
  %_SetValueOf(this, value);
});


%FunctionSetPrototype($Date, new $Date($NaN));


var WeekDays = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat'];
var Months = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'];


function TwoDigitString(value) {
  return value < 10 ? "0" + value : "" + value;
}


function DateString(time) {
  return WeekDays[WeekDay(time)] + ' '
      + Months[MonthFromTime(time)] + ' '
      + TwoDigitString(DateFromTime(time)) + ' '
      + YearFromTime(time);
}


var LongWeekDays = ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday'];
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 TimeString(time) {
  return TwoDigitString(HOUR_FROM_TIME(time)) + ':'
      + TwoDigitString(MIN_FROM_TIME(time)) + ':'
      + TwoDigitString(SEC_FROM_TIME(time));
}


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;
  }

  var timezoneOffset =
      (DaylightSavingsOffset(time) + local_time_offset) / msPerMinute;
  var sign = (timezoneOffset >= 0) ? 1 : -1;
  var hours = FLOOR((sign * timezoneOffset)/60);
  var min   = FLOOR((sign * timezoneOffset)%60);
  var gmt = ' GMT' + ((sign == 1) ? '+' : '-') +
      TwoDigitString(hours) + TwoDigitString(min);
  return gmt + ' (' +  timezone + ')';
}


function DatePrintString(time) {
  return DateString(time) + ' ' + TimeString(time);
}

// -------------------------------------------------------------------

// Reused output buffer. Used when parsing date strings.
var parse_buffer = $Array(8);

// ECMA 262 - 15.9.4.2
function DateParse(string) {
  var arr = %DateParseString(ToString(string), parse_buffer);
  if (IS_NULL(arr)) return $NaN;

  var day = MakeDay(arr[0], arr[1], arr[2]);
  var time = MakeTime(arr[3], arr[4], arr[5], arr[6]);
  var date = MakeDate(day, time);

  if (IS_NULL(arr[7])) {
    return TimeClip(UTC(date));
  } else {
    return TimeClip(date - arr[7] * 1000);
  }
}


// ECMA 262 - 15.9.4.3
function DateUTC(year, month, date, hours, minutes, seconds, ms) {
  year = ToNumber(year);
  month = ToNumber(month);
  var argc = %_ArgumentsLength();
  date = argc > 2 ? ToNumber(date) : 1;
  hours = argc > 3 ? ToNumber(hours) : 0;
  minutes = argc > 4 ? ToNumber(minutes) : 0;
  seconds = argc > 5 ? ToNumber(seconds) : 0;
  ms = argc > 6 ? ToNumber(ms) : 0;
  year = (!NUMBER_IS_NAN(year) && 0 <= TO_INTEGER(year) && TO_INTEGER(year) <= 99)
      ? 1900 + TO_INTEGER(year) : year;
  var day = MakeDay(year, month, date);
  var time = MakeTime(hours, minutes, seconds, ms);
  return %_SetValueOf(this, TimeClip(MakeDate(day, time)));
}


// Mozilla-specific extension. Returns the number of milliseconds
// elapsed since 1 January 1970 00:00:00 UTC.
function DateNow() {
  return %DateCurrentTime();
}


// ECMA 262 - 15.9.5.2
function DateToString() {
  var t = 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;
}


// ECMA 262 - 15.9.5.3
function DateToDateString() {
  var t = DATE_VALUE(this);
  if (NUMBER_IS_NAN(t)) return kInvalidDate;
  return DateString(LocalTimeNoCheck(t));
}


// ECMA 262 - 15.9.5.4
function DateToTimeString() {
  var t = 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;
}


// ECMA 262 - 15.9.5.5
function DateToLocaleString() {
  return %_CallFunction(this, DateToString);
}


// ECMA 262 - 15.9.5.6
function DateToLocaleDateString() {
  var t = DATE_VALUE(this);
  if (NUMBER_IS_NAN(t)) return kInvalidDate;
  return LongDateString(LocalTimeNoCheck(t));
}


// ECMA 262 - 15.9.5.7
function DateToLocaleTimeString() {
  var t = DATE_VALUE(this);
  if (NUMBER_IS_NAN(t)) return kInvalidDate;
  var lt = LocalTimeNoCheck(t);
  return TimeString(lt);
}


// ECMA 262 - 15.9.5.8
function DateValueOf() {
  return DATE_VALUE(this);
}


// ECMA 262 - 15.9.5.9
function DateGetTime() {
  return DATE_VALUE(this);
}


// ECMA 262 - 15.9.5.10
function DateGetFullYear() {
  var t = DATE_VALUE(this);
  if (NUMBER_IS_NAN(t)) return t;
  var cache = Date_cache;
  if (cache.time === t) return cache.year;
  return YearFromTime(LocalTimeNoCheck(t));
}


// ECMA 262 - 15.9.5.11
function DateGetUTCFullYear() {
  var t = DATE_VALUE(this);
  if (NUMBER_IS_NAN(t)) return t;
  return YearFromTime(t);
}


// ECMA 262 - 15.9.5.12
function DateGetMonth() {
  var t = DATE_VALUE(this);
  if (NUMBER_IS_NAN(t)) return t;
  return MonthFromTime(LocalTimeNoCheck(t));
}


// ECMA 262 - 15.9.5.13
function DateGetUTCMonth() {
  var t = DATE_VALUE(this);
  if (NUMBER_IS_NAN(t)) return t;
  return MonthFromTime(t);
}


// ECMA 262 - 15.9.5.14
function DateGetDate() {
  var t = DATE_VALUE(this);
  if (NUMBER_IS_NAN(t)) return t;
  return DateFromTime(LocalTimeNoCheck(t));
}


// ECMA 262 - 15.9.5.15
function DateGetUTCDate() {
  var t = DATE_VALUE(this);
  return NAN_OR_DATE_FROM_TIME(t);
}


// ECMA 262 - 15.9.5.16
function DateGetDay() {
  var t = DATE_VALUE(this);
  if (NUMBER_IS_NAN(t)) return t;
  return WeekDay(LocalTimeNoCheck(t));
}


// ECMA 262 - 15.9.5.17
function DateGetUTCDay() {
  var t = DATE_VALUE(this);
  if (NUMBER_IS_NAN(t)) return t;
  return WeekDay(t);
}


// ECMA 262 - 15.9.5.18
function DateGetHours() {
  var t = DATE_VALUE(this);
  if (NUMBER_IS_NAN(t)) return t;
  return HOUR_FROM_TIME(LocalTimeNoCheck(t));
}


// 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);
}


// ECMA 262 - 15.9.5.20
function DateGetMinutes() {
  var t = DATE_VALUE(this);
  if (NUMBER_IS_NAN(t)) return t;
  return MIN_FROM_TIME(LocalTimeNoCheck(t));
}


// ECMA 262 - 15.9.5.21
function DateGetUTCMinutes() {
  var t = DATE_VALUE(this);
  return NAN_OR_MIN_FROM_TIME(t);
}


// ECMA 262 - 15.9.5.22
function DateGetSeconds() {
  var t = DATE_VALUE(this);
  if (NUMBER_IS_NAN(t)) return t;
  return SEC_FROM_TIME(LocalTimeNoCheck(t));
}


// ECMA 262 - 15.9.5.23
function DateGetUTCSeconds() {
  var t = DATE_VALUE(this);
  return NAN_OR_SEC_FROM_TIME(t);
}


// 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));
}


// ECMA 262 - 15.9.5.25
function DateGetUTCMilliseconds() {
  var t = DATE_VALUE(this);
  return NAN_OR_MS_FROM_TIME(t);
}


// 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;
}


// ECMA 262 - 15.9.5.27
function DateSetTime(ms) {
  if (!IS_DATE(this)) ThrowDateTypeError();
  return %_SetValueOf(this, TimeClip(ToNumber(ms)));
}


// ECMA 262 - 15.9.5.28
function DateSetMilliseconds(ms) {
  var t = LocalTime(DATE_VALUE(this));
  ms = ToNumber(ms);
  var time = MakeTime(HOUR_FROM_TIME(t), MIN_FROM_TIME(t), SEC_FROM_TIME(t), ms);
  return %_SetValueOf(this, TimeClip(UTC(MakeDate(DAY(t), time))));
}


// ECMA 262 - 15.9.5.29
function DateSetUTCMilliseconds(ms) {
  var t = DATE_VALUE(this);
  ms = ToNumber(ms);
  var time = MakeTime(HOUR_FROM_TIME(t), MIN_FROM_TIME(t), SEC_FROM_TIME(t), ms);
  return %_SetValueOf(this, TimeClip(MakeDate(DAY(t), time)));
}


// ECMA 262 - 15.9.5.30
function DateSetSeconds(sec, ms) {
  var t = LocalTime(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 %_SetValueOf(this, TimeClip(UTC(MakeDate(DAY(t), time))));
}


// ECMA 262 - 15.9.5.31
function DateSetUTCSeconds(sec, ms) {
  var t = 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 %_SetValueOf(this, TimeClip(MakeDate(DAY(t), time)));
}


// ECMA 262 - 15.9.5.33
function DateSetMinutes(min, sec, ms) {
  var t = LocalTime(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 %_SetValueOf(this, TimeClip(UTC(MakeDate(DAY(t), time))));
}


// ECMA 262 - 15.9.5.34
function DateSetUTCMinutes(min, sec, ms) {
  var t = 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 %_SetValueOf(this, TimeClip(MakeDate(DAY(t), time)));
}


// ECMA 262 - 15.9.5.35
function DateSetHours(hour, min, sec, ms) {
  var t = LocalTime(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);
  var time = MakeTime(hour, min, sec, ms);
  return %_SetValueOf(this, TimeClip(UTC(MakeDate(DAY(t), time))));
}


// ECMA 262 - 15.9.5.34
function DateSetUTCHours(hour, min, sec, ms) {
  var t = 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);
  var time = MakeTime(hour, min, sec, ms);
  return %_SetValueOf(this, TimeClip(MakeDate(DAY(t), time)));
}


// ECMA 262 - 15.9.5.36
function DateSetDate(date) {
  var t = LocalTime(DATE_VALUE(this));
  date = ToNumber(date);
  var day = MakeDay(YearFromTime(t), MonthFromTime(t), date);
  return %_SetValueOf(this, TimeClip(UTC(MakeDate(day, TimeWithinDay(t)))));
}


// ECMA 262 - 15.9.5.37
function DateSetUTCDate(date) {
  var t = DATE_VALUE(this);
  date = ToNumber(date);
  var day = MakeDay(YearFromTime(t), MonthFromTime(t), date);
  return %_SetValueOf(this, TimeClip(MakeDate(day, TimeWithinDay(t))));
}


// ECMA 262 - 15.9.5.38
function DateSetMonth(month, date) {
  var t = LocalTime(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 %_SetValueOf(this, TimeClip(UTC(MakeDate(day, TimeWithinDay(t)))));
}


// ECMA 262 - 15.9.5.39
function DateSetUTCMonth(month, date) {
  var t = 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 %_SetValueOf(this, TimeClip(MakeDate(day, TimeWithinDay(t))));
}


// ECMA 262 - 15.9.5.40
function DateSetFullYear(year, month, date) {
  var t = DATE_VALUE(this);
  t = NUMBER_IS_NAN(t) ? 0 : LocalTimeNoCheck(t);
  year = ToNumber(year);
  var argc = %_ArgumentsLength();
  month = argc < 2 ? MonthFromTime(t) : ToNumber(month);
  date = argc < 3 ? DateFromTime(t) : ToNumber(date);
  var day = MakeDay(year, month, date);
  return %_SetValueOf(this, TimeClip(UTC(MakeDate(day, TimeWithinDay(t)))));
}


// 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();
  year = ToNumber(year);
  month = argc < 2 ? MonthFromTime(t) : ToNumber(month);
  date = argc < 3 ? DateFromTime(t) : ToNumber(date);
  var day = MakeDay(year, month, date);
  return %_SetValueOf(this, TimeClip(MakeDate(day, TimeWithinDay(t))));
}


// ECMA 262 - 15.9.5.42
function DateToUTCString() {
  var t = 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';
}


// ECMA 262 - B.2.4
function DateGetYear() {
  var t = DATE_VALUE(this);
  if (NUMBER_IS_NAN(t)) return $NaN;
  return YearFromTime(LocalTimeNoCheck(t)) - 1900;
}


// ECMA 262 - B.2.5
function DateSetYear(year) {
  var t = LocalTime(DATE_VALUE(this));
  if (NUMBER_IS_NAN(t)) t = 0;
  year = ToNumber(year);
  if (NUMBER_IS_NAN(year)) return %_SetValueOf(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 %_SetValueOf(this, TimeClip(UTC(MakeDate(day, TimeWithinDay(t)))));
}


// ECMA 262 - B.2.6
//
// Notice that this does not follow ECMA 262 completely.  ECMA 262
// says that toGMTString should be the same Function object as
// toUTCString.  JSC does not do this, so for compatibility we do not
// do that either.  Instead, we create a new function whose name
// property will return toGMTString.
function DateToGMTString() {
  return %_CallFunction(this, DateToUTCString);
}


function PadInt(n, digits) {
  if (digits == 1) return n;
  return n < MathPow(10, digits - 1) ? '0' + PadInt(n, digits - 1) : n;
}


function DateToISOString() {
  var t = DATE_VALUE(this);
  if (NUMBER_IS_NAN(t)) return kInvalidDate;
  var year = this.getUTCFullYear();
  var year_string;
  if (year >= 0 && year <= 9999) {
    year_string = PadInt(year, 4);
  } else {
    if (year < 0) {
      year_string = "-" + PadInt(-year, 6);
    } else {
      year_string = "+" + PadInt(year, 6);
    }
  }
  return year_string +
      '-' + PadInt(this.getUTCMonth() + 1, 2) +
      '-' + PadInt(this.getUTCDate(), 2) +
      'T' + PadInt(this.getUTCHours(), 2) +
      ':' + PadInt(this.getUTCMinutes(), 2) +
      ':' + PadInt(this.getUTCSeconds(), 2) +
      '.' + PadInt(this.getUTCMilliseconds(), 3) +
      'Z';
}


function DateToJSON(key) {
  var o = ToObject(this);
  var tv = DefaultNumber(o);
  if (IS_NUMBER(tv) && !NUMBER_IS_FINITE(tv)) {
    return null;
  }
  return o.toISOString();
}


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;
}


// -------------------------------------------------------------------

function SetupDate() {
  // Setup non-enumerable properties of the Date object itself.
  InstallFunctions($Date, DONT_ENUM, $Array(
    "UTC", DateUTC,
    "parse", DateParse,
    "now", DateNow
  ));

  // Setup non-enumerable constructor property of the Date prototype object.
  %SetProperty($Date.prototype, "constructor", $Date, DONT_ENUM);

  // Setup non-enumerable functions of the Date prototype object and
  // set their names.
  InstallFunctionsOnHiddenPrototype($Date.prototype, DONT_ENUM, $Array(
    "toString", DateToString,
    "toDateString", DateToDateString,
    "toTimeString", DateToTimeString,
    "toLocaleString", DateToLocaleString,
    "toLocaleDateString", DateToLocaleDateString,
    "toLocaleTimeString", DateToLocaleTimeString,
    "valueOf", DateValueOf,
    "getTime", DateGetTime,
    "getFullYear", DateGetFullYear,
    "getUTCFullYear", DateGetUTCFullYear,
    "getMonth", DateGetMonth,
    "getUTCMonth", DateGetUTCMonth,
    "getDate", DateGetDate,
    "getUTCDate", DateGetUTCDate,
    "getDay", DateGetDay,
    "getUTCDay", DateGetUTCDay,
    "getHours", DateGetHours,
    "getUTCHours", DateGetUTCHours,
    "getMinutes", DateGetMinutes,
    "getUTCMinutes", DateGetUTCMinutes,
    "getSeconds", DateGetSeconds,
    "getUTCSeconds", DateGetUTCSeconds,
    "getMilliseconds", DateGetMilliseconds,
    "getUTCMilliseconds", DateGetUTCMilliseconds,
    "getTimezoneOffset", DateGetTimezoneOffset,
    "setTime", DateSetTime,
    "setMilliseconds", DateSetMilliseconds,
    "setUTCMilliseconds", DateSetUTCMilliseconds,
    "setSeconds", DateSetSeconds,
    "setUTCSeconds", DateSetUTCSeconds,
    "setMinutes", DateSetMinutes,
    "setUTCMinutes", DateSetUTCMinutes,
    "setHours", DateSetHours,
    "setUTCHours", DateSetUTCHours,
    "setDate", DateSetDate,
    "setUTCDate", DateSetUTCDate,
    "setMonth", DateSetMonth,
    "setUTCMonth", DateSetUTCMonth,
    "setFullYear", DateSetFullYear,
    "setUTCFullYear", DateSetUTCFullYear,
    "toGMTString", DateToGMTString,
    "toUTCString", DateToUTCString,
    "getYear", DateGetYear,
    "setYear", DateSetYear,
    "toISOString", DateToISOString,
    "toJSON", DateToJSON
  ));
}

SetupDate();