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// Copyright (c) 2011, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
part of dart.core;
/// An instant in time, such as July 20, 1969, 8:18pm GMT.
///
/// DateTimes can represent time values that are at a distance of at most
/// 100,000,000 days from epoch (1970-01-01 UTC): -271821-04-20 to 275760-09-13.
///
/// Create a DateTime object by using one of the constructors
/// or by parsing a correctly formatted string,
/// which complies with a subset of ISO 8601.
/// Note that hours are specified between 0 and 23,
/// as in a 24-hour clock.
/// For example:
///
/// ```
/// var now = DateTime.now();
/// var berlinWallFell = DateTime.utc(1989, 11, 9);
/// var moonLanding = DateTime.parse("1969-07-20 20:18:04Z"); // 8:18pm
/// ```
///
/// A DateTime object is anchored either in the UTC time zone
/// or in the local time zone of the current computer
/// when the object is created.
///
/// Once created, neither the value nor the time zone
/// of a DateTime object may be changed.
///
/// You can use properties to get
/// the individual units of a DateTime object.
///
/// ```
/// assert(berlinWallFell.month == 11);
/// assert(moonLanding.hour == 20);
/// ```
///
/// For convenience and readability,
/// the DateTime class provides a constant for each day and month
/// name - for example, [august] and [friday].
/// You can use these constants to improve code readability:
///
/// ```
/// var berlinWallFell = DateTime.utc(1989, DateTime.november, 9);
/// assert(berlinWallFell.weekday == DateTime.thursday);
/// ```
///
/// Day and month values begin at 1, and the week starts on Monday.
/// That is, the constants [january] and [monday] are both 1.
///
/// ## Working with UTC and local time
///
/// A DateTime object is in the local time zone
/// unless explicitly created in the UTC time zone.
///
/// ```
/// var dDay = DateTime.utc(1944, 6, 6);
/// ```
///
/// Use [isUtc] to determine whether a DateTime object is based in UTC.
/// Use the methods [toLocal] and [toUtc]
/// to get the equivalent date/time value specified in the other time zone.
/// Use [timeZoneName] to get an abbreviated name of the time zone
/// for the DateTime object.
/// To find the difference
/// between UTC and the time zone of a DateTime object
/// call [timeZoneOffset].
///
/// ## Comparing DateTime objects
///
/// The DateTime class contains several handy methods,
/// such as [isAfter], [isBefore], and [isAtSameMomentAs],
/// for comparing DateTime objects.
///
/// ```
/// assert(berlinWallFell.isAfter(moonLanding) == true);
/// assert(berlinWallFell.isBefore(moonLanding) == false);
/// ```
///
/// ## Using DateTime with Duration
///
/// Use the [add] and [subtract] methods with a [Duration] object
/// to create a DateTime object based on another.
/// For example, to find the date that is sixty days (24 * 60 hours) after today,
/// write:
///
/// ```
/// var now = DateTime.now();
/// var sixtyDaysFromNow = now.add(const Duration(days: 60));
/// ```
///
/// To find out how much time is between two DateTime objects use
/// [difference], which returns a [Duration] object:
///
/// ```
/// var difference = berlinWallFell.difference(moonLanding);
/// assert(difference.inDays == 7416);
/// ```
///
/// The difference between two dates in different time zones
/// is just the number of nanoseconds between the two points in time.
/// It doesn't take calendar days into account.
/// That means that the difference between two midnights in local time may be
/// less than 24 hours times the number of days between them,
/// if there is a daylight saving change in between.
/// If the difference above is calculated using Australian local time, the
/// difference is 7415 days and 23 hours, which is only 7415 whole days as
/// reported by `inDays`.
///
/// ## Other resources
///
/// See [Duration] to represent a span of time.
/// See [Stopwatch] to measure timespans.
///
/// The DateTime class does not provide internationalization.
/// To internationalize your code, use
/// the [intl](https://pub.dev/packages/intl) package.
///
class DateTime implements Comparable<DateTime> {
// Weekday constants that are returned by [weekday] method:
static const int monday = 1;
static const int tuesday = 2;
static const int wednesday = 3;
static const int thursday = 4;
static const int friday = 5;
static const int saturday = 6;
static const int sunday = 7;
static const int daysPerWeek = 7;
// Month constants that are returned by the [month] getter.
static const int january = 1;
static const int february = 2;
static const int march = 3;
static const int april = 4;
static const int may = 5;
static const int june = 6;
static const int july = 7;
static const int august = 8;
static const int september = 9;
static const int october = 10;
static const int november = 11;
static const int december = 12;
static const int monthsPerYear = 12;
/// The value of this DateTime.
///
/// The content of this field is implementation dependent. On JavaScript it is
/// equal to [millisecondsSinceEpoch]. On the VM it is equal to
/// [microsecondsSinceEpoch].
final int _value;
/// True if this [DateTime] is set to UTC time.
///
/// ```
/// var dDay = DateTime.utc(1944, 6, 6);
/// assert(dDay.isUtc);
/// ```
///
final bool isUtc;
/// Constructs a [DateTime] instance specified in the local time zone.
///
/// For example,
/// to create a DateTime object representing the 7th of September 2017,
/// 5:30pm
///
/// ```
/// var dentistAppointment = DateTime(2017, 9, 7, 17, 30);
/// ```
DateTime(int year,
[int month = 1,
int day = 1,
int hour = 0,
int minute = 0,
int second = 0,
int millisecond = 0,
int microsecond = 0])
: this._internal(year, month, day, hour, minute, second, millisecond,
microsecond, false);
/// Constructs a [DateTime] instance specified in the UTC time zone.
///
/// ```
/// var moonLanding = DateTime.utc(1969, 7, 20, 20, 18, 04);
/// ```
///
/// When dealing with dates or historic events prefer to use UTC DateTimes,
/// since they are unaffected by daylight-saving changes and are unaffected
/// by the local timezone.
DateTime.utc(int year,
[int month = 1,
int day = 1,
int hour = 0,
int minute = 0,
int second = 0,
int millisecond = 0,
int microsecond = 0])
: this._internal(year, month, day, hour, minute, second, millisecond,
microsecond, true);
/// Constructs a [DateTime] instance with current date and time in the
/// local time zone.
///
/// ```
/// var thisInstant = DateTime.now();
/// ```
DateTime.now() : this._now();
/// Constructs a new [DateTime] instance based on [formattedString].
///
/// Throws a [FormatException] if the input string cannot be parsed.
///
/// The function parses a subset of ISO 8601
/// which includes the subset accepted by RFC 3339.
///
/// The accepted inputs are currently:
///
/// * A date: A signed four-to-six digit year, two digit month and
/// two digit day, optionally separated by `-` characters.
/// Examples: "19700101", "-0004-12-24", "81030-04-01".
/// * An optional time part, separated from the date by either `T` or a space.
/// The time part is a two digit hour,
/// then optionally a two digit minutes value,
/// then optionally a two digit seconds value, and
/// then optionally a '.' or ',' followed by at least a one digit
/// second fraction.
/// The minutes and seconds may be separated from the previous parts by a
/// ':'.
/// Examples: "12", "12:30:24.124", "12:30:24,124", "123010.50".
/// * An optional time-zone offset part,
/// possibly separated from the previous by a space.
/// The time zone is either 'z' or 'Z', or it is a signed two digit hour
/// part and an optional two digit minute part. The sign must be either
/// "+" or "-", and can not be omitted.
/// The minutes may be separated from the hours by a ':'.
/// Examples: "Z", "-10", "+01:30", "+1130".
///
/// This includes the output of both [toString] and [toIso8601String], which
/// will be parsed back into a `DateTime` object with the same time as the
/// original.
///
/// The result is always in either local time or UTC.
/// If a time zone offset other than UTC is specified,
/// the time is converted to the equivalent UTC time.
///
/// Examples of accepted strings:
///
/// * `"2012-02-27"`
/// * `"2012-02-27 13:27:00"`
/// * `"2012-02-27 13:27:00.123456789z"`
/// * `"2012-02-27 13:27:00,123456789z"`
/// * `"20120227 13:27:00"`
/// * `"20120227T132700"`
/// * `"20120227"`
/// * `"+20120227"`
/// * `"2012-02-27T14Z"`
/// * `"2012-02-27T14+00:00"`
/// * `"-123450101 00:00:00 Z"`: in the year -12345.
/// * `"2002-02-27T14:00:00-0500"`: Same as `"2002-02-27T19:00:00Z"`
// TODO(lrn): restrict incorrect values like 2003-02-29T50:70:80.
// Or not, that may be a breaking change.
static DateTime parse(String formattedString) {
var re = _parseFormat;
Match? match = re.firstMatch(formattedString);
if (match != null) {
int parseIntOrZero(String? matched) {
if (matched == null) return 0;
return int.parse(matched);
}
// Parses fractional second digits of '.(\d+)' into the combined
// microseconds. We only use the first 6 digits because of DateTime
// precision of 999 milliseconds and 999 microseconds.
int parseMilliAndMicroseconds(String? matched) {
if (matched == null) return 0;
int length = matched.length;
assert(length >= 1);
int result = 0;
for (int i = 0; i < 6; i++) {
result *= 10;
if (i < matched.length) {
result += matched.codeUnitAt(i) ^ 0x30;
}
}
return result;
}
int years = int.parse(match[1]!);
int month = int.parse(match[2]!);
int day = int.parse(match[3]!);
int hour = parseIntOrZero(match[4]);
int minute = parseIntOrZero(match[5]);
int second = parseIntOrZero(match[6]);
int milliAndMicroseconds = parseMilliAndMicroseconds(match[7]);
int millisecond =
milliAndMicroseconds ~/ Duration.microsecondsPerMillisecond;
int microsecond = milliAndMicroseconds
.remainder(Duration.microsecondsPerMillisecond) as int;
bool isUtc = false;
if (match[8] != null) {
// timezone part
isUtc = true;
String? tzSign = match[9];
if (tzSign != null) {
// timezone other than 'Z' and 'z'.
int sign = (tzSign == '-') ? -1 : 1;
int hourDifference = int.parse(match[10]!);
int minuteDifference = parseIntOrZero(match[11]);
minuteDifference += 60 * hourDifference;
minute -= sign * minuteDifference;
}
}
int? value = _brokenDownDateToValue(years, month, day, hour, minute,
second, millisecond, microsecond, isUtc);
if (value == null) {
throw FormatException("Time out of range", formattedString);
}
return DateTime._withValue(value, isUtc: isUtc);
} else {
throw FormatException("Invalid date format", formattedString);
}
}
/// Constructs a new [DateTime] instance based on [formattedString].
///
/// Works like [parse] except that this function returns `null`
/// where [parse] would throw a [FormatException].
static DateTime? tryParse(String formattedString) {
// TODO: Optimize to avoid throwing.
try {
return parse(formattedString);
} on FormatException {
return null;
}
}
static const int _maxMillisecondsSinceEpoch = 8640000000000000;
/// Constructs a new [DateTime] instance
/// with the given [millisecondsSinceEpoch].
///
/// If [isUtc] is false then the date is in the local time zone.
///
/// The constructed [DateTime] represents
/// 1970-01-01T00:00:00Z + [millisecondsSinceEpoch] ms in the given
/// time zone (local or UTC).
external DateTime.fromMillisecondsSinceEpoch(int millisecondsSinceEpoch,
{bool isUtc = false});
/// Constructs a new [DateTime] instance
/// with the given [microsecondsSinceEpoch].
///
/// If [isUtc] is false then the date is in the local time zone.
///
/// The constructed [DateTime] represents
/// 1970-01-01T00:00:00Z + [microsecondsSinceEpoch] us in the given
/// time zone (local or UTC).
external DateTime.fromMicrosecondsSinceEpoch(int microsecondsSinceEpoch,
{bool isUtc = false});
/// Constructs a new [DateTime] instance with the given value.
///
/// If [isUtc] is false then the date is in the local time zone.
DateTime._withValue(this._value, {required this.isUtc}) {
if (millisecondsSinceEpoch.abs() > _maxMillisecondsSinceEpoch ||
(millisecondsSinceEpoch.abs() == _maxMillisecondsSinceEpoch &&
microsecond != 0)) {
throw ArgumentError(
"DateTime is outside valid range: $millisecondsSinceEpoch");
}
// For backwards compatibility with legacy mode.
checkNotNullable(isUtc, "isUtc");
}
/// Returns true if [other] is a [DateTime] at the same moment and in the
/// same time zone (UTC or local).
///
/// ```
/// var dDayUtc = DateTime.utc(1944, 6, 6);
/// var dDayLocal = dDayUtc.toLocal();
///
/// // These two dates are at the same moment, but are in different zones.
/// assert(dDayUtc != dDayLocal);
/// ```
///
/// See [isAtSameMomentAs] for a comparison that compares moments in time
/// independently of their zones.
external bool operator ==(Object other);
/// Returns true if [this] occurs before [other].
///
/// The comparison is independent
/// of whether the time is in UTC or in the local time zone.
///
/// ```
/// var now = DateTime.now();
/// var earlier = now.subtract(const Duration(seconds: 5));
/// assert(earlier.isBefore(now));
/// assert(!now.isBefore(now));
///
/// // This relation stays the same, even when changing timezones.
/// assert(earlier.isBefore(now.toUtc()));
/// assert(earlier.toUtc().isBefore(now));
///
/// assert(!now.toUtc().isBefore(now));
/// assert(!now.isBefore(now.toUtc()));
/// ```
external bool isBefore(DateTime other);
/// Returns true if [this] occurs after [other].
///
/// The comparison is independent
/// of whether the time is in UTC or in the local time zone.
///
/// ```
/// var now = DateTime.now();
/// var later = now.add(const Duration(seconds: 5));
/// assert(later.isAfter(now));
/// assert(!now.isBefore(now));
///
/// // This relation stays the same, even when changing timezones.
/// assert(later.isAfter(now.toUtc()));
/// assert(later.toUtc().isAfter(now));
///
/// assert(!now.toUtc().isBefore(now));
/// assert(!now.isBefore(now.toUtc()));
/// ```
external bool isAfter(DateTime other);
/// Returns true if [this] occurs at the same moment as [other].
///
/// The comparison is independent of whether the time is in UTC or in the local
/// time zone.
///
/// ```
/// var now = DateTime.now();
/// var later = now.add(const Duration(seconds: 5));
/// assert(!later.isAtSameMomentAs(now));
/// assert(now.isAtSameMomentAs(now));
///
/// // This relation stays the same, even when changing timezones.
/// assert(!later.isAtSameMomentAs(now.toUtc()));
/// assert(!later.toUtc().isAtSameMomentAs(now));
///
/// assert(now.toUtc().isAtSameMomentAs(now));
/// assert(now.isAtSameMomentAs(now.toUtc()));
/// ```
external bool isAtSameMomentAs(DateTime other);
/// Compares this DateTime object to [other],
/// returning zero if the values are equal.
///
/// Returns a negative value if this DateTime [isBefore] [other]. It returns 0
/// if it [isAtSameMomentAs] [other], and returns a positive value otherwise
/// (when this [isAfter] [other]).
external int compareTo(DateTime other);
int get hashCode => (_value ^ (_value >> 30)) & 0x3FFFFFFF;
/// Returns this DateTime value in the local time zone.
///
/// Returns [this] if it is already in the local time zone.
/// Otherwise this method is equivalent to:
///
/// ```
/// DateTime.fromMicrosecondsSinceEpoch(microsecondsSinceEpoch,
/// isUtc: false)
/// ```
DateTime toLocal() {
if (isUtc) {
return DateTime._withValue(_value, isUtc: false);
}
return this;
}
/// Returns this DateTime value in the UTC time zone.
///
/// Returns [this] if it is already in UTC.
/// Otherwise this method is equivalent to:
///
/// ```
/// DateTime.fromMicrosecondsSinceEpoch(microsecondsSinceEpoch,
/// isUtc: true)
/// ```
DateTime toUtc() {
if (isUtc) return this;
return DateTime._withValue(_value, isUtc: true);
}
static String _fourDigits(int n) {
int absN = n.abs();
String sign = n < 0 ? "-" : "";
if (absN >= 1000) return "$n";
if (absN >= 100) return "${sign}0$absN";
if (absN >= 10) return "${sign}00$absN";
return "${sign}000$absN";
}
static String _sixDigits(int n) {
assert(n < -9999 || n > 9999);
int absN = n.abs();
String sign = n < 0 ? "-" : "+";
if (absN >= 100000) return "$sign$absN";
return "${sign}0$absN";
}
static String _threeDigits(int n) {
if (n >= 100) return "${n}";
if (n >= 10) return "0${n}";
return "00${n}";
}
static String _twoDigits(int n) {
if (n >= 10) return "${n}";
return "0${n}";
}
/// Returns a human-readable string for this instance.
///
/// The returned string is constructed for the time zone of this instance.
/// The `toString()` method provides a simply formatted string.
/// It does not support internationalized strings.
/// Use the [intl](https://pub.dev/packages/intl) package
/// at the pub shared packages repo.
///
/// The resulting string can be parsed back using [parse].
String toString() {
String y = _fourDigits(year);
String m = _twoDigits(month);
String d = _twoDigits(day);
String h = _twoDigits(hour);
String min = _twoDigits(minute);
String sec = _twoDigits(second);
String ms = _threeDigits(millisecond);
String us = microsecond == 0 ? "" : _threeDigits(microsecond);
if (isUtc) {
return "$y-$m-$d $h:$min:$sec.$ms${us}Z";
} else {
return "$y-$m-$d $h:$min:$sec.$ms$us";
}
}
/// Returns an ISO-8601 full-precision extended format representation.
///
/// The format is `yyyy-MM-ddTHH:mm:ss.mmmuuuZ` for UTC time, and
/// `yyyy-MM-ddTHH:mm:ss.mmmuuu` (no trailing "Z") for local/non-UTC time,
/// where:
///
/// * `yyyy` is a, possibly negative, four digit representation of the year,
/// if the year is in the range -9999 to 9999,
/// otherwise it is a signed six digit representation of the year.
/// * `MM` is the month in the range 01 to 12,
/// * `dd` is the day of the month in the range 01 to 31,
/// * `HH` are hours in the range 00 to 23,
/// * `mm` are minutes in the range 00 to 59,
/// * `ss` are seconds in the range 00 to 59 (no leap seconds),
/// * `mmm` are milliseconds in the range 000 to 999, and
/// * `uuu` are microseconds in the range 001 to 999. If [microsecond] equals
/// 0, then this part is omitted.
///
/// The resulting string can be parsed back using [parse].
String toIso8601String() {
String y =
(year >= -9999 && year <= 9999) ? _fourDigits(year) : _sixDigits(year);
String m = _twoDigits(month);
String d = _twoDigits(day);
String h = _twoDigits(hour);
String min = _twoDigits(minute);
String sec = _twoDigits(second);
String ms = _threeDigits(millisecond);
String us = microsecond == 0 ? "" : _threeDigits(microsecond);
if (isUtc) {
return "$y-$m-${d}T$h:$min:$sec.$ms${us}Z";
} else {
return "$y-$m-${d}T$h:$min:$sec.$ms$us";
}
}
/// Returns a new [DateTime] instance with [duration] added to [this].
///
/// ```
/// var today = DateTime.now();
/// var fiftyDaysFromNow = today.add(const Duration(days: 50));
/// ```
///
/// Notice that the duration being added is actually 50 * 24 * 60 * 60
/// seconds. If the resulting `DateTime` has a different daylight saving offset
/// than `this`, then the result won't have the same time-of-day as `this`, and
/// may not even hit the calendar date 50 days later.
///
/// Be careful when working with dates in local time.
external DateTime add(Duration duration);
/// Returns a new [DateTime] instance with [duration] subtracted from [this].
///
/// ```
/// DateTime today = DateTime.now();
/// DateTime fiftyDaysAgo = today.subtract(const Duration(days: 50));
/// ```
///
/// Notice that the duration being subtracted is actually 50 * 24 * 60 * 60
/// seconds. If the resulting `DateTime` has a different daylight saving offset
/// than `this`, then the result won't have the same time-of-day as `this`, and
/// may not even hit the calendar date 50 days earlier.
///
/// Be careful when working with dates in local time.
external DateTime subtract(Duration duration);
/// Returns a [Duration] with the difference when subtracting [other] from
/// [this].
///
/// The returned [Duration] will be negative if [other] occurs after [this].
///
/// ```
/// var berlinWallFell = DateTime.utc(1989, DateTime.november, 9);
/// var dDay = DateTime.utc(1944, DateTime.june, 6);
///
/// Duration difference = berlinWallFell.difference(dDay);
/// assert(difference.inDays == 16592);
/// ```
///
/// The difference is measured in seconds and fractions of seconds.
/// The difference above counts the number of fractional seconds between
/// midnight at the beginning of those dates.
/// If the dates above had been in local time, not UTC, then the difference
/// between two midnights may not be a multiple of 24 hours due to daylight
/// saving differences.
///
/// For example, in Australia, similar code using local time instead of UTC:
///
/// ```
/// var berlinWallFell = DateTime(1989, DateTime.november, 9);
/// var dDay = DateTime(1944, DateTime.june, 6);
/// Duration difference = berlinWallFell.difference(dDay);
/// assert(difference.inDays == 16592);
/// ```
/// will fail because the difference is actually 16591 days and 23 hours, and
/// [Duration.inDays] only returns the number of whole days.
external Duration difference(DateTime other);
external DateTime._internal(int year, int month, int day, int hour,
int minute, int second, int millisecond, int microsecond, bool isUtc);
external DateTime._now();
/// Returns the time as value (millisecond or microsecond since epoch), or
/// null if the values are out of range.
external static int? _brokenDownDateToValue(
int year,
int month,
int day,
int hour,
int minute,
int second,
int millisecond,
int microsecond,
bool isUtc);
/// The number of milliseconds since
/// the "Unix epoch" 1970-01-01T00:00:00Z (UTC).
///
/// This value is independent of the time zone.
///
/// This value is at most
/// 8,640,000,000,000,000ms (100,000,000 days) from the Unix epoch.
/// In other words: `millisecondsSinceEpoch.abs() <= 8640000000000000`.
external int get millisecondsSinceEpoch;
/// The number of microseconds since
/// the "Unix epoch" 1970-01-01T00:00:00Z (UTC).
///
/// This value is independent of the time zone.
///
/// This value is at most
/// 8,640,000,000,000,000,000us (100,000,000 days) from the Unix epoch.
/// In other words: `microsecondsSinceEpoch.abs() <= 8640000000000000000`.
///
/// Note that this value does not fit into 53 bits (the size of a IEEE double).
/// A JavaScript number is not able to hold this value.
external int get microsecondsSinceEpoch;
/// The time zone name.
///
/// This value is provided by the operating system and may be an
/// abbreviation or a full name.
///
/// In the browser or on Unix-like systems commonly returns abbreviations,
/// such as "CET" or "CEST". On Windows returns the full name, for example
/// "Pacific Standard Time".
external String get timeZoneName;
/// The time zone offset, which
/// is the difference between local time and UTC.
///
/// The offset is positive for time zones east of UTC.
///
/// Note, that JavaScript, Python and C return the difference between UTC and
/// local time. Java, C# and Ruby return the difference between local time and
/// UTC.
external Duration get timeZoneOffset;
/// The year.
///
/// ```
/// var moonLanding = DateTime.parse("1969-07-20 20:18:04Z");
/// assert(moonLanding.year == 1969);
/// ```
external int get year;
/// The month [1..12].
///
/// ```
/// var moonLanding = DateTime.parse("1969-07-20 20:18:04Z");
/// assert(moonLanding.month == 7);
/// assert(moonLanding.month == DateTime.july);
/// ```
external int get month;
/// The day of the month [1..31].
///
/// ```
/// var moonLanding = DateTime.parse("1969-07-20 20:18:04Z");
/// assert(moonLanding.day == 20);
/// ```
external int get day;
/// The hour of the day, expressed as in a 24-hour clock [0..23].
///
/// ```
/// var moonLanding = DateTime.parse("1969-07-20 20:18:04Z");
/// assert(moonLanding.hour == 20);
/// ```
external int get hour;
/// The minute [0...59].
///
/// ```
/// var moonLanding = DateTime.parse("1969-07-20 20:18:04Z");
/// assert(moonLanding.minute == 18);
/// ```
external int get minute;
/// The second [0...59].
///
/// ```
/// var moonLanding = DateTime.parse("1969-07-20 20:18:04Z");
/// assert(moonLanding.second == 4);
/// ```
external int get second;
/// The millisecond [0...999].
///
/// ```
/// var moonLanding = DateTime.parse("1969-07-20 20:18:04Z");
/// assert(moonLanding.millisecond == 0);
/// ```
external int get millisecond;
/// The microsecond [0...999].
///
/// ```
/// var moonLanding = DateTime.parse("1969-07-20 20:18:04Z");
/// assert(moonLanding.microsecond == 0);
/// ```
external int get microsecond;
/// The day of the week [monday]..[sunday].
///
/// In accordance with ISO 8601
/// a week starts with Monday, which has the value 1.
///
/// ```
/// var moonLanding = DateTime.parse("1969-07-20 20:18:04Z");
/// assert(moonLanding.weekday == 7);
/// assert(moonLanding.weekday == DateTime.sunday);
/// ```
external int get weekday;
/*
* date ::= yeardate time_opt timezone_opt
* yeardate ::= year colon_opt month colon_opt day
* year ::= sign_opt digit{4,6}
* colon_opt :: <empty> | ':'
* sign ::= '+' | '-'
* sign_opt ::= <empty> | sign
* month ::= digit{2}
* day ::= digit{2}
* time_opt ::= <empty> | (' ' | 'T') hour minutes_opt
* minutes_opt ::= <empty> | colon_opt digit{2} seconds_opt
* seconds_opt ::= <empty> | colon_opt digit{2} millis_opt
* micros_opt ::= <empty> | ('.' | ',') digit+
* timezone_opt ::= <empty> | space_opt timezone
* space_opt :: ' ' | <empty>
* timezone ::= 'z' | 'Z' | sign digit{2} timezonemins_opt
* timezonemins_opt ::= <empty> | colon_opt digit{2}
*/
static final RegExp _parseFormat =
RegExp(r'^([+-]?\d{4,6})-?(\d\d)-?(\d\d)' // Day part.
r'(?:[ T](\d\d)(?::?(\d\d)(?::?(\d\d)(?:[.,](\d+))?)?)?' // Time part.
r'( ?[zZ]| ?([-+])(\d\d)(?::?(\d\d))?)?)?$'); // Timezone part.
}