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// Copyright (c) 2012, 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 intl;
// TODO(efortuna): Customized pattern system -- suggested by i18n needs
// feedback on appropriateness.
* DateFormat is for formatting and parsing dates in a locale-sensitive
* manner.
* It allows the user to choose from a set of standard date time formats as well
* as specify a customized pattern under certain locales. Date elements that
* vary across locales include month name, week name, field order, etc.
* We also allow the user to use any customized pattern to parse or format
* date-time strings under certain locales. Date elements that vary across
* locales include month name, weekname, field, order, etc.
* Formatting dates in the default "en_US" format does not require any
* initialization. e.g.
* print(new DateFormat.yMMMd().format(new;
* But for other locales, the formatting data for the locale must be
* obtained. This can currently be done
* in one of three ways, determined by which library you import. In all cases,
* the "initializeDateFormatting" method must be called and will return a future
* that is complete once the locale data is available. The result of the future
* isn't important, but the data for that locale is available to the date
* formatting and parsing once it completes.
* The easiest option is that the data may be available locally, imported in a
* library that contains data for all the locales.
* import 'package:intl/date_symbol_data_local.dart';
* initializeDateFormatting("fr_FR", null).then((_) => runMyCode());
* If we are running outside of a browser, we may want to read the data
* from files in the file system.
* import 'package:intl/date_symbol_data_file.dart';
* initializeDateFormatting("de_DE", null).then((_) => runMyCode());
* If we are running in a browser, we may want to read the data from the
* server using the XmlHttpRequest mechanism.
* import 'package:intl/date_symbol_data_http_request.dart';
* initializeDateFormatting("pt_BR", null).then((_) => runMyCode());
* The code in example/basic/basic_example.dart shows a full example of
* using this mechanism.
* Once we have the locale data, we need to specify the particular format.
* This library uses the ICU/JDK date/time pattern specification both for
* complete format specifications and also the abbreviated "skeleton" form
* which can also adapt to different locales and is preferred where available.
* Skeletons: These can be specified either as the ICU constant name or as the
* skeleton to which it resolves. The supported set of skeletons is as follows
* ICU Name Skeleton
* -------- --------
* DAY d
* YEAR y
* HOUR24 H
* HOUR j
* HOUR_TZ jz
* Examples Using the US Locale:
* Pattern Result
* ---------------- -------
* new DateFormat.yMd() -> 7/10/1996
* new DateFormat("yMd") -> 7/10/1996
* new DateFormat.yMMMMd("en_US") -> July 10, 1996
* new DateFormat("Hm", "en_US") -> 12:08 PM
* new DateFormat.yMd().add_Hm() -> 7/10/1996 12:08 PM
* Explicit Pattern Syntax: Formats can also be specified with a pattern string.
* The skeleton forms will resolve to explicit patterns of this form, but will
* also adapt to different patterns in different locales.
* The following characters are reserved:
* Symbol Meaning Presentation Example
* ------ ------- ------------ -------
* G era designator (Text) AD
* y year (Number) 1996
* M month in year (Text & Number) July & 07
* L standalone month (Text & Number) July & 07
* d day in month (Number) 10
* c standalone day (Number) 10
* h hour in am/pm (1~12) (Number) 12
* H hour in day (0~23) (Number) 0
* m minute in hour (Number) 30
* s second in minute (Number) 55
* S fractional second (Number) 978
* E day of week (Text) Tuesday
* D day in year (Number) 189
* a am/pm marker (Text) PM
* k hour in day (1~24) (Number) 24
* K hour in am/pm (0~11) (Number) 0
* z time zone (Text) Pacific Standard Time
* Z time zone (RFC 822) (Number) -0800
* v time zone (generic) (Text) Pacific Time
* Q quarter (Text) Q3
* ' escape for text (Delimiter) 'Date='
* '' single quote (Literal) 'o''clock'
* The count of pattern letters determine the format.
* **Text**:
* * 5 pattern letters--use narrow form for standalone. Otherwise does not apply
* * 4 or more pattern letters--use full form,
* * 3 pattern letters--use short or abbreviated form if one exists
* * less than 3--use numeric form if one exists
* **Number**: the minimum number of digits. Shorter numbers are zero-padded to
* this amount (e.g. if "m" produces "6", "mm" produces "06"). Year is handled
* specially; that is, if the count of 'y' is 2, the Year will be truncated to
* 2 digits. (e.g., if "yyyy" produces "1997", "yy" produces "97".) Unlike other
* fields, fractional seconds are padded on the right with zero.
* **(Text & Number)**: 3 or over, use text, otherwise use number.
* Any characters not in the pattern will be treated as quoted text. For
* instance, characters like ':', '.', ' ', '#' and '@' will appear in the
* resulting text even though they are not enclosed in single quotes. In our
* current pattern usage, not all letters have meanings. But those unused
* letters are strongly discouraged to be used as quoted text without quotes,
* because we may use other letters as pattern characters in the future.
* Examples Using the US Locale:
* Format Pattern Result
* -------------- -------
* "yyyy.MM.dd G 'at' HH:mm:ss vvvv" 1996.07.10 AD at 15:08:56 Pacific Time
* "EEE, MMM d, ''yy" Wed, July 10, '96
* "h:mm a" 12:08 PM
* "hh 'o''clock' a, zzzz" 12 o'clock PM, Pacific Daylight Time
* "K:mm a, vvv" 0:00 PM, PT
* "yyyyy.MMMMM.dd GGG hh:mm aaa" 01996.July.10 AD 12:08 PM
* When parsing a date string using the abbreviated year pattern ("yy"),
* DateFormat must interpret the abbreviated year relative to some
* century. It does this by adjusting dates to be within 80 years before and 20
* years after the time the parse function is called. For example, using a
* pattern of "MM/dd/yy" and a DateParse instance created on Jan 1, 1997,
* the string "01/11/12" would be interpreted as Jan 11, 2012 while the string
* "05/04/64" would be interpreted as May 4, 1964. During parsing, only
* strings consisting of exactly two digits, as defined by {@link
* java.lang.Character#isDigit(char)}, will be parsed into the default
* century. Any other numeric string, such as a one digit string, a three or
* more digit string will be interpreted as its face value.
* If the year pattern does not have exactly two 'y' characters, the year is
* interpreted literally, regardless of the number of digits. So using the
* pattern "MM/dd/yyyy", "01/11/12" parses to Jan 11, 12 A.D.
class DateFormat {
* Creates a new DateFormat, using the format specified by [newPattern]. For
* forms that match one of our predefined skeletons, we look up the
* corresponding pattern in [locale] (or in the default locale if none is
* specified) and use the resulting full format string. This is the
* preferred usage, but if [newPattern] does not match one of the skeletons,
* then it is used as a format directly, but will not be adapted to suit
* the locale.
* For example, in an en_US locale, specifying the skeleton
* new DateFormat('yMEd');
* or the explicit
* new DateFormat('EEE, M/d/y');
* would produce the same result, a date of the form
* Wed, 6/27/2012
* The first version would produce a different format string if used in
* another locale, but the second format would always be the same.
* If [locale] does not exist in our set of supported locales then an
* [ArgumentError] is thrown.
DateFormat([String newPattern, String locale]) {
// TODO(alanknight): It should be possible to specify multiple skeletons eg
// date, time, timezone all separately. Adding many or named parameters to
// the constructor seems awkward, especially with the possibility of
// confusion with the locale. A "fluent" interface with cascading on an
// instance might work better? A list of patterns is also possible.
_locale = Intl.verifiedLocale(locale, localeExists);
* Return a string representing [date] formatted according to our locale
* and internal format.
String format(DateTime date) {
// TODO(efortuna): read optional TimeZone argument (or similar)?
var result = new StringBuffer();
_formatFields.forEach((field) => result.write(field.format(date)));
return result.toString();
* Returns a date string indicating how long ago (3 hours, 2 minutes)
* something has happened or how long in the future something will happen
* given a [reference] DateTime relative to the current time.
String formatDuration(DateTime reference) {
return '';
* Formats a string indicating how long ago (negative [duration]) or how far
* in the future (positive [duration]) some time is with respect to a
* reference [date].
String formatDurationFrom(Duration duration, DateTime date) {
return '';
* Given user input, attempt to parse the [inputString] into the anticipated
* format, treating it as being in the local timezone.
DateTime parse(String inputString, [utc = false]) {
// TODO(alanknight): The Closure code refers to special parsing of numeric
// values with no delimiters, which we currently don't do. Should we?
var dateFields = new _DateBuilder();
if (utc) dateFields.utc=true;
var stream = new _Stream(inputString);
(each) => each.parse(stream, dateFields));
return dateFields.asDate();
* Given user input, attempt to parse the [inputString] into the anticipated
* format, treating it as being in UTC.
DateTime parseUTC(String inputString) {
return parse(inputString, true);
* Return the locale code in which we operate, e.g. 'en_US' or 'pt'.
String get locale => _locale;
* Returns a list of all locales for which we have date formatting
* information.
static List<String> allLocalesWithSymbols() => dateTimeSymbols.keys.toList();
* The named constructors for this class are all conveniences for creating
* instances using one of the known "skeleton" formats, and having code
* completion support for discovering those formats.
* So,
* new DateFormat.yMd("en_US")
* is equivalent to
* new DateFormat("yMd", "en_US")
* To create a compound format you can use these constructors in combination
* with the add_ methods below. e.g.
* new DateFormat.yMd().add_Hms();
* If the optional [locale] is omitted, the format will be created using the
* default locale in [Intl.systemLocale].
DateFormat.d([locale]) : this("d", locale);
DateFormat.E([locale]) : this("E", locale);
DateFormat.EEEE([locale]) : this("EEEE", locale);
DateFormat.LLL([locale]) : this("LLL", locale);
DateFormat.LLLL([locale]) : this("LLLL", locale);
DateFormat.M([locale]) : this("M", locale);
DateFormat.Md([locale]) : this("Md", locale);
DateFormat.MEd([locale]) : this("MEd", locale);
DateFormat.MMM([locale]) : this("MMM", locale);
DateFormat.MMMd([locale]) : this("MMMd", locale);
DateFormat.MMMEd([locale]) : this("MMMEd", locale);
DateFormat.MMMM([locale]) : this("MMMM", locale);
DateFormat.MMMMd([locale]) : this("MMMMd", locale);
DateFormat.MMMMEEEEd([locale]) : this("MMMMEEEEd", locale);
DateFormat.QQQ([locale]) : this("QQQ", locale);
DateFormat.QQQQ([locale]) : this("QQQQ", locale);
DateFormat.y([locale]) : this("y", locale);
DateFormat.yM([locale]) : this("yM", locale);
DateFormat.yMd([locale]) : this("yMd", locale);
DateFormat.yMEd([locale]) : this("yMEd", locale);
DateFormat.yMMM([locale]) : this("yMMM", locale);
DateFormat.yMMMd([locale]) : this("yMMMd", locale);
DateFormat.yMMMEd([locale]) : this("yMMMEd", locale);
DateFormat.yMMMM([locale]) : this("yMMMM", locale);
DateFormat.yMMMMd([locale]) : this("yMMMMd", locale);
DateFormat.yMMMMEEEEd([locale]) : this("yMMMMEEEEd", locale);
DateFormat.yQQQ([locale]) : this("yQQQ", locale);
DateFormat.yQQQQ([locale]) : this("yQQQQ", locale);
DateFormat.H([locale]) : this("H", locale);
DateFormat.Hm([locale]) : this("Hm", locale);
DateFormat.Hms([locale]) : this("Hms", locale);
DateFormat.j([locale]) : this("j", locale);[locale]) : this("jm", locale);
DateFormat.jms([locale]) : this("jms", locale);
DateFormat.jmv([locale]) : this("jmv", locale);
DateFormat.jmz([locale]) : this("jmz", locale);
DateFormat.jv([locale]) : this("jv", locale);
DateFormat.jz([locale]) : this("jz", locale);
DateFormat.m([locale]) : this("m", locale);[locale]) : this("ms", locale);
DateFormat.s([locale]) : this("s", locale);
* The "add_*" methods append a particular skeleton to the format, or set
* it as the only format if none was previously set. These are primarily
* useful for creating compound formats. For example
* new DateFormat.yMd().add_Hms();
* would create a date format that prints both the date and the time.
DateFormat add_d() => addPattern("d");
DateFormat add_E() => addPattern("E");
DateFormat add_EEEE() => addPattern("EEEE");
DateFormat add_LLL() => addPattern("LLL");
DateFormat add_LLLL() => addPattern("LLLL");
DateFormat add_M() => addPattern("M");
DateFormat add_Md() => addPattern("Md");
DateFormat add_MEd() => addPattern("MEd");
DateFormat add_MMM() => addPattern("MMM");
DateFormat add_MMMd() => addPattern("MMMd");
DateFormat add_MMMEd() => addPattern("MMMEd");
DateFormat add_MMMM() => addPattern("MMMM");
DateFormat add_MMMMd() => addPattern("MMMMd");
DateFormat add_MMMMEEEEd() => addPattern("MMMMEEEEd");
DateFormat add_QQQ() => addPattern("QQQ");
DateFormat add_QQQQ() => addPattern("QQQQ");
DateFormat add_y() => addPattern("y");
DateFormat add_yM() => addPattern("yM");
DateFormat add_yMd() => addPattern("yMd");
DateFormat add_yMEd() => addPattern("yMEd");
DateFormat add_yMMM() => addPattern("yMMM");
DateFormat add_yMMMd() => addPattern("yMMMd");
DateFormat add_yMMMEd() => addPattern("yMMMEd");
DateFormat add_yMMMM() => addPattern("yMMMM");
DateFormat add_yMMMMd() => addPattern("yMMMMd");
DateFormat add_yMMMMEEEEd() => addPattern("yMMMMEEEEd");
DateFormat add_yQQQ() => addPattern("yQQQ");
DateFormat add_yQQQQ() => addPattern("yQQQQ");
DateFormat add_H() => addPattern("H");
DateFormat add_Hm() => addPattern("Hm");
DateFormat add_Hms() => addPattern("Hms");
DateFormat add_j() => addPattern("j");
DateFormat add_jm() => addPattern("jm");
DateFormat add_jms() => addPattern("jms");
DateFormat add_jmv() => addPattern("jmv");
DateFormat add_jmz() => addPattern("jmz");
DateFormat add_jv() => addPattern("jv");
DateFormat add_jz() => addPattern("jz");
DateFormat add_m() => addPattern("m");
DateFormat add_ms() => addPattern("ms");
DateFormat add_s() => addPattern("s");
* For each of the skeleton formats we also allow the use of the corresponding
* ICU constant names.
static const String ABBR_MONTH = 'MMM';
static const String DAY = 'd';
static const String ABBR_WEEKDAY = 'E';
static const String WEEKDAY = 'EEEE';
static const String ABBR_STANDALONE_MONTH = 'LLL';
static const String STANDALONE_MONTH = 'LLLL';
static const String NUM_MONTH = 'M';
static const String NUM_MONTH_DAY = 'Md';
static const String NUM_MONTH_WEEKDAY_DAY = 'MEd';
static const String ABBR_MONTH_DAY = 'MMMd';
static const String ABBR_MONTH_WEEKDAY_DAY = 'MMMEd';
static const String MONTH = 'MMMM';
static const String MONTH_DAY = 'MMMMd';
static const String MONTH_WEEKDAY_DAY = 'MMMMEEEEd';
static const String ABBR_QUARTER = 'QQQ';
static const String QUARTER = 'QQQQ';
static const String YEAR = 'y';
static const String YEAR_NUM_MONTH = 'yM';
static const String YEAR_NUM_MONTH_DAY = 'yMd';
static const String YEAR_NUM_MONTH_WEEKDAY_DAY = 'yMEd';
static const String YEAR_ABBR_MONTH = 'yMMM';
static const String YEAR_ABBR_MONTH_DAY = 'yMMMd';
static const String YEAR_ABBR_MONTH_WEEKDAY_DAY = 'yMMMEd';
static const String YEAR_MONTH = 'yMMMM';
static const String YEAR_MONTH_DAY = 'yMMMMd';
static const String YEAR_MONTH_WEEKDAY_DAY = 'yMMMMEEEEd';
static const String YEAR_ABBR_QUARTER = 'yQQQ';
static const String YEAR_QUARTER = 'yQQQQ';
static const String HOUR24 = 'H';
static const String HOUR24_MINUTE = 'Hm';
static const String HOUR24_MINUTE_SECOND = 'Hms';
static const String HOUR = 'j';
static const String HOUR_MINUTE = 'jm';
static const String HOUR_MINUTE_SECOND = 'jms';
static const String HOUR_MINUTE_GENERIC_TZ = 'jmv';
static const String HOUR_MINUTE_TZ = 'jmz';
static const String HOUR_GENERIC_TZ = 'jv';
static const String HOUR_TZ = 'jz';
static const String MINUTE = 'm';
static const String MINUTE_SECOND = 'ms';
static const String SECOND = 's';
/** The locale in which we operate, e.g. 'en_US', or 'pt'. */
String _locale;
* The full template string. This may have been specified directly, or
* it may have been derived from a skeleton and the locale information
* on how to interpret that skeleton.
String _pattern;
* We parse the format string into individual [_DateFormatField] objects
* that are used to do the actual formatting and parsing. Do not use
* this variable directly, use the getter [_formatFields].
List<_DateFormatField> _formatFieldsPrivate;
* Getter for [_formatFieldsPrivate] that lazily initializes it.
get _formatFields {
if (_formatFieldsPrivate == null) {
if (_pattern == null) _useDefaultPattern();
_formatFieldsPrivate = parsePattern(_pattern);
return _formatFieldsPrivate;
* We are being asked to do formatting without having set any pattern.
* Use a default.
_useDefaultPattern() {
* A series of regular expressions used to parse a format string into its
* component fields.
static List<RegExp> _matchers = [
// Quoted String - anything between single quotes, with escaping
// of single quotes by doubling them.
// e.g. in the pattern "hh 'o''clock'" will match 'o''clock'
new RegExp("^\'(?:[^\']|\'\')*\'"),
// Fields - any sequence of 1 or more of the same field characters.
// e.g. in "hh:mm:ss" will match hh, mm, and ss. But in "hms" would
// match each letter individually.
new RegExp(
// Everything else - A sequence that is not quotes or field characters.
// e.g. in "hh:mm:ss" will match the colons.
new RegExp("^[^\'GyMkSEahKHcLQdmsvzZ]+")
* Set our pattern, appending it to any existing patterns. Also adds a single
* space to separate the two.
_appendPattern(String inputPattern, [String separator = ' ']) {
if (_pattern == null) {
_pattern = inputPattern;
} else {
_pattern = "$_pattern$separator$inputPattern";
* Add [inputPattern] to this instance as a pattern. If there was a previous
* pattern, then this appends to it, separating the two by [separator].
* [inputPattern] is first looked up in our list of known skeletons.
* If it's found there, then use the corresponding pattern for this locale.
* If it's not, then treat [inputPattern] as an explicit pattern.
DateFormat addPattern(String inputPattern, [String separator = ' ']) {
// TODO(alanknight): This is an expensive operation. Caching recently used
// formats, or possibly introducing an entire "locale" object that would
// cache patterns for that locale could be a good optimization.
// If we have already parsed the format fields, reset them.
_formatFieldsPrivate = null;
if (inputPattern == null) return this;
if (!_availableSkeletons.containsKey(inputPattern)) {
_appendPattern(inputPattern, separator);
} else {
_appendPattern(_availableSkeletons[inputPattern], separator);
return this;
/** Return the pattern that we use to format dates.*/
get pattern => _pattern;
/** Return the skeletons for our current locale. */
Map get _availableSkeletons {
return dateTimePatterns[locale];
* Return the [DateSymbol] information for the locale. This can be useful
* to find lists like the names of weekdays or months in a locale, but
* the structure of this data may change, and it's generally better to go
* through the [format] and [parse] APIs. If the locale isn't present, or
* is uninitialized, returns null;
DateSymbols get dateSymbols => dateTimeSymbols[_locale];
* Set the locale. If the locale can't be found, we also look up
* based on alternative versions, e.g. if we have no 'en_CA' we will
* look for 'en' as a fallback. It will also translate en-ca into en_CA.
* Null is also considered a valid value for [newLocale], indicating
* to use the default.
_setLocale(String newLocale) {
_locale = Intl.verifiedLocale(newLocale, localeExists);
* Return true if the locale exists, or if it is null. The null case
* is interpreted to mean that we use the default locale.
static bool localeExists(localeName) {
if (localeName == null) return false;
return dateTimeSymbols.containsKey(localeName);
static List get _fieldConstructors => [
(pattern, parent) => new _DateFormatQuotedField(pattern, parent),
(pattern, parent) => new _DateFormatPatternField(pattern, parent),
(pattern, parent) => new _DateFormatLiteralField(pattern, parent)];
/** Parse the template pattern and return a list of field objects.*/
List parsePattern(String pattern) {
if (pattern == null) return null;
return _parsePatternHelper(pattern).reversed.toList();
/** Recursive helper for parsing the template pattern. */
List _parsePatternHelper(String pattern) {
if (pattern.isEmpty) return [];
var matched = _match(pattern);
if (matched == null) return [];
var parsed = _parsePatternHelper(
return parsed;
/** Find elements in a string that are patterns for specific fields.*/
_DateFormatField _match(String pattern) {
for (var i = 0; i < _matchers.length; i++) {
var regex = _matchers[i];
var match = regex.firstMatch(pattern);
if (match != null) {
return _fieldConstructors[i](, this);