Canonical Vocabulary

The canonical vocabulary is the dialect-agnostic set of date-field meanings every conversion routes through. It is the join key for the whole reference: a dialect maps each of its tokens to a canonical member (Token Mapping), and a library declares the canonical fields it renders (Libraries). Nothing here depends on how many dialects exist.

Values are stable field/style[/qualifier] identifiers exported as the Canonical object — the optional qualifier (e.g. iso, the hour cycle h12, standalone, space-padded) refines a base field/style, and its absence is the default. When a value carries more than one qualifier, identity qualifiers (iso, the hour cycle) come before presentation ones (space-padded, lower). The order is fixed; see the Contributing guide. Prefer the named members (Canonical.YearNumeric) over the raw strings. To split a symbol into those parts programmatically, see decodeCanonical.

Adding a member is a minor, additive change; renaming or removing one is breaking. A dialect or library only ever references these members — it never references another dialect.

Era

Member	Value	Meaning
`EraAbbreviated`	`era/abbreviated`	Era, abbreviated (e.g. AD)
`EraWide`	`era/wide`	Era, wide (e.g. Anno Domini)
`EraNarrow`	`era/narrow`	Era, narrow (single character)

Calendar year

Member	Value	Meaning
`YearNumeric`	`year/numeric`	Calendar year, full
`YearTwoDigit`	`year/2-digit`	Calendar year, 2-digit

Century

The high-order two digits of the year, e.g. 2026 → 20.

Member	Value	Meaning
`CenturyTwoDigit`	`century/2-digit`	Century, 2-digit

Week-numbering year

The year that owns a given week — local or ISO.

Member	Value	Meaning
`WeekYearNumeric`	`week-year/numeric`	Local week-numbering year, full
`WeekYearTwoDigit`	`week-year/2-digit`	Local week-numbering year, 2-digit
`WeekYearNumericIso`	`week-year/numeric/iso`	ISO week-numbering year, full
`WeekYearTwoDigitIso`	`week-year/2-digit/iso`	ISO week-numbering year, 2-digit

Quarter

Member	Value	Meaning
`QuarterNumeric`	`quarter/numeric`	Quarter
`QuarterTwoDigit`	`quarter/2-digit`	Quarter, 2-digit
`QuarterOrdinal`	`quarter/ordinal`	Quarter, ordinal
`QuarterAbbreviated`	`quarter/abbreviated`	Quarter name, abbreviated
`QuarterWide`	`quarter/wide`	Quarter name, wide
`QuarterNarrow`	`quarter/narrow`	Quarter name, narrow
`QuarterAbbreviatedStandalone`	`quarter/abbreviated/standalone`	Quarter name, abbreviated, stand-alone
`QuarterWideStandalone`	`quarter/wide/standalone`	Quarter name, wide, stand-alone
`QuarterNarrowStandalone`	`quarter/narrow/standalone`	Quarter name, narrow, stand-alone

Month

Member	Value	Meaning
`MonthNumeric`	`month/numeric`	Month
`MonthTwoDigit`	`month/2-digit`	Month, 2-digit
`MonthTwoDigitSpacePadded`	`month/2-digit/space-padded`	Month, 2-digit, blank-padded
`MonthOrdinal`	`month/ordinal`	Month, ordinal
`MonthAbbreviated`	`month/abbreviated`	Month name, abbreviated
`MonthWide`	`month/wide`	Month name, wide
`MonthNarrow`	`month/narrow`	Month name, narrow
`MonthAbbreviatedStandalone`	`month/abbreviated/standalone`	Month name, abbreviated, stand-alone
`MonthWideStandalone`	`month/wide/standalone`	Month name, wide, stand-alone
`MonthNarrowStandalone`	`month/narrow/standalone`	Month name, narrow, stand-alone

Week of year

Member	Value	Meaning
`WeekOfYearNumeric`	`week-of-year/numeric`	Local week of year
`WeekOfYearTwoDigit`	`week-of-year/2-digit`	Local week of year, 2-digit
`WeekOfYearOrdinal`	`week-of-year/ordinal`	Local week of year, ordinal
`WeekOfYearNumericIso`	`week-of-year/numeric/iso`	ISO week of year
`WeekOfYearTwoDigitIso`	`week-of-year/2-digit/iso`	ISO week of year, 2-digit
`WeekOfYearTwoDigitIsoSpacePadded`	`week-of-year/2-digit/iso/space-padded`	ISO week of year, 2-digit, blank-padded
`WeekOfYearOrdinalIso`	`week-of-year/ordinal/iso`	ISO week of year, ordinal

Day of month

Member	Value	Meaning
`DayOfMonthNumeric`	`day-of-month/numeric`	Day of month
`DayOfMonthTwoDigit`	`day-of-month/2-digit`	Day of month, 2-digit (zero-padded)
`DayOfMonthTwoDigitSpacePadded`	`day-of-month/2-digit/space-padded`	Day of month, 2-digit, blank-padded
`DayOfMonthOrdinal`	`day-of-month/ordinal`	Day of month, ordinal

Day of year

Member	Value	Meaning
`DayOfYearNumeric`	`day-of-year/numeric`	Day of year
`DayOfYearTwoDigit`	`day-of-year/2-digit`	Day of year, 2-digit
`DayOfYearThreeDigit`	`day-of-year/3-digit`	Day of year, 3-digit
`DayOfYearThreeDigitSpacePadded`	`day-of-year/3-digit/space-padded`	Day of year, 3-digit, blank-padded
`DayOfYearOrdinal`	`day-of-year/ordinal`	Day of year, ordinal

Weekday name

Member	Value	Meaning
`WeekdayAbbreviated`	`weekday/abbreviated`	Weekday name, abbreviated
`WeekdayWide`	`weekday/wide`	Weekday name, wide
`WeekdayNarrow`	`weekday/narrow`	Weekday name, narrow
`WeekdayShort`	`weekday/short`	Weekday name, short
`WeekdayAbbreviatedStandalone`	`weekday/abbreviated/standalone`	Weekday name, abbreviated, stand-alone
`WeekdayWideStandalone`	`weekday/wide/standalone`	Weekday name, wide, stand-alone
`WeekdayNarrowStandalone`	`weekday/narrow/standalone`	Weekday name, narrow, stand-alone
`WeekdayShortStandalone`	`weekday/short/standalone`	Weekday name, short, stand-alone

Weekday number

Member	Value	Meaning
`WeekdayNumeric`	`weekday/numeric`	Weekday as a number, locale-dependent
`WeekdayTwoDigit`	`weekday/2-digit`	Weekday as a number, 2-digit, locale-dependent
`WeekdayNumericIso`	`weekday/numeric/iso`	Weekday as a number, ISO (1 = Monday)

Day period

Member	Value	Meaning
`DayPeriodAbbreviated`	`day-period/abbreviated`	AM/PM, abbreviated
`DayPeriodAbbreviatedLower`	`day-period/abbreviated/lower`	AM/PM, abbreviated, forced lowercase
`DayPeriodWide`	`day-period/wide`	AM/PM, wide
`DayPeriodNarrow`	`day-period/narrow`	AM/PM, narrow
`DayPeriodAbbreviatedExtended`	`day-period/abbreviated/extended`	Day period with noon/midnight, abbreviated
`DayPeriodWideExtended`	`day-period/wide/extended`	Day period with noon/midnight, wide
`DayPeriodNarrowExtended`	`day-period/narrow/extended`	Day period with noon/midnight, narrow
`DayPeriodAbbreviatedFlexible`	`day-period/abbreviated/flexible`	Flexible day period (in the morning, …), abbreviated
`DayPeriodWideFlexible`	`day-period/wide/flexible`	Flexible day period, wide
`DayPeriodNarrowFlexible`	`day-period/narrow/flexible`	Flexible day period, narrow

Hour

Member	Value	Meaning
`HourNumericH12`	`hour/numeric/h12`	Hour 1–12
`HourTwoDigitH12`	`hour/2-digit/h12`	Hour 1–12, 2-digit
`HourTwoDigitH12SpacePadded`	`hour/2-digit/h12/space-padded`	Hour 1–12, 2-digit, blank-padded
`HourNumericH23`	`hour/numeric/h23`	Hour 0–23
`HourTwoDigitH23`	`hour/2-digit/h23`	Hour 0–23, 2-digit
`HourTwoDigitH23SpacePadded`	`hour/2-digit/h23/space-padded`	Hour 0–23, 2-digit, blank-padded
`HourNumericH24`	`hour/numeric/h24`	Hour 1–24
`HourTwoDigitH24`	`hour/2-digit/h24`	Hour 1–24, 2-digit
`HourNumericH11`	`hour/numeric/h11`	Hour 0–11
`HourTwoDigitH11`	`hour/2-digit/h11`	Hour 0–11, 2-digit

Minute & second

Member	Value	Meaning
`MinuteNumeric`	`minute/numeric`	Minute
`MinuteTwoDigit`	`minute/2-digit`	Minute, 2-digit
`MinuteTwoDigitSpacePadded`	`minute/2-digit/space-padded`	Minute, 2-digit, blank-padded
`SecondNumeric`	`second/numeric`	Second
`SecondTwoDigit`	`second/2-digit`	Second, 2-digit
`SecondTwoDigitSpacePadded`	`second/2-digit/space-padded`	Second, 2-digit, blank-padded
`FractionalSecond1`	`fractional-second/1`	Fractional second, 1 digit
`FractionalSecond2`	`fractional-second/2`	Fractional second, 2 digits
`FractionalSecond3`	`fractional-second/3`	Fractional second, 3 digits

Time zone & offset

Member	Value	Meaning
`TimezoneAbbreviated`	`timezone/abbreviated`	Time-zone name
`OffsetWithColon`	`offset/with-colon`	UTC offset, `±hh:mm`
`OffsetWithoutColon`	`offset/without-colon`	UTC offset, `±hhmm`
`OffsetWithColonZulu`	`offset/with-colon/zulu`	UTC offset, `±hh:mm`, `Z` at zero
`OffsetWithoutColonZulu`	`offset/without-colon/zulu`	UTC offset, `±hhmm`, `Z` at zero

Unix epoch

Member	Value	Meaning
`EpochSeconds`	`epoch/seconds`	Seconds since the Unix epoch
`EpochMilliseconds`	`epoch/milliseconds`	Milliseconds since the Unix epoch

Localized presets

Deferred to the library’s locale at format time, so they map preset ↔ preset — never expanded to a concrete pattern (which would hardcode one locale). See Libraries → Localized presets.

Member	Value	Meaning
`LocalizedDateShort`	`localized-date/short`	Localized date, short
`LocalizedDateMedium`	`localized-date/medium`	Localized date, medium
`LocalizedDateLong`	`localized-date/long`	Localized date, long
`LocalizedDateFull`	`localized-date/full`	Localized date, full (with weekday)
`LocalizedTimeShort`	`localized-time/short`	Localized time, short
`LocalizedTimeMedium`	`localized-time/medium`	Localized time, with seconds
`LocalizedTimeLong`	`localized-time/long`	Localized time, with time zone
`LocalizedTimeFull`	`localized-time/full`	Localized time, full
`LocalizedDateTimeShort`	`localized-date-time/short`	Localized date + time, short
`LocalizedDateTimeMedium`	`localized-date-time/medium`	Localized date + time, medium
`LocalizedDateTimeLong`	`localized-date-time/long`	Localized date + time, long
`LocalizedDateTimeFull`	`localized-date-time/full`	Localized date + time, full