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JS TutorialLesson #214

Temporal Standards

Temporal is based on the following standards:

Name	Description
ISO 8601 Date/Time	International standard
ISO 8601 Duration	ISO 8601 duration codes
RFC 3339 Date/Time	Internet standard
RFC 9557 Date/Time	Temporal standard
RFC 5545 iCalendar	The iCalendar data format
JavaScript Calendars	Internet calendar systems

The ISO 8601 Standard

ISO 8601 is the International Standard for representing dates and times.

It is a machine-readable text format in the form YYYY-MM-DDThh:mm:ssZ.

ISO 8601 was designed to eliminate confusion caused by regional date variations.

It follows a "largest to smallest" hierarchy (year, month, day, hour, minute, second) which ensures that dates are alphabetically sortable.

Note > ISO 8601 avoids confusion between regional formats like: > MM/DD/YYYY (US format) > DD/MM/YYYY (European format)

ISO 8601 Strings

An ISO 8601 string represents dates and times in a structured and sortable format:

Format	Description
YYYY	A 4-digit year
MM	2-digit month
DD	2-digit day
T	Separator for time
hh	Hour
mm	Minute
ss	Second
Z	Zero (Zulu) time Zone

Examples

Format	Format	Example
Date (4-digit year)	YYYY-MM-DD	2026-05-17
Time (24 hour)	hh:mm:ss	14:30:00
Date & Time	YYYY-MM-DDThh:mm:ssZ	2026-05-17T14:30:00Z
Date & Time UTC	YYYY-MM-DDThh:mm:ssZ	2026-05-17T14:30:00Z
Date & Time + Offset	YYYY-MM-DDThh:mm:ss±hh:mm	2026-05-17T14:30:00+01:00
Week Date	YYYY-Www-D	2026-W20-7
Ordinal (001-366)	YYYY-nnn	2026-074

ISO 8601 Duration Codes

An ISO 8601 duration represent lengths of time.

It uses a standard format starting with ±P (Period), followed by the structure nYnMnDTnHnMnS.

Code	Description
±	Optional positive/negative duration (default is +).
P	Duration designator (for period)
nY	Number of calendar years
nM	Number of calendar months
nW	Number of weeks
nD	Number of calendar days
T	Time designator (precedes time components)
nH	Number of hours
nM	Number of minutes
nS	Number of seconds

Syntax

Example Code

javascript

Try it Yourself

&plusmn;P nY nM nW nD T nH nM nS

Example

Example Code

javascript

Try it Yourself

P3Y6M4DT12H30M5S

More Examples

Duration	Code
1 Day	P1D
45 Minutes	PT45M
1 Year, 2 Months, 3 Days	P1Y2M3D
4 Hours, 5 Minutes, 6 Seconds	PT4H5M6S
2.5 Hours	PT2H30M
5 Weeks	P5W

Usage Rules

Time Separator If you have hours, minutes, or seconds, you must use the T separator, or the code will be invalid (e.g. PT3H not P3H).
Optionality Components are optional, but at least one must be present after P or T.
Order The order must be preserved: P-> Y-> M-> W-> D-> T-> H-> M-> S.
Decimal fractions You can use decimal points for the smallest unit, like PT0.0021S for 2.1 milliseconds.

The RF 3339 Format

RFC 3339 is the Internet Standard for Date and Time Formats.

It is a Subset of ISO 8601 designed for use in Internet protocols.

Feature	Description
Format	Follows the ISO pattern YYYY-MM-DDThh:mm:ssZ
Time Zones	Requires a Z for time zone UTC or an offset (+05:00)
T Separator	Allows the "T" separator to be replaced by " " for readability
Web APIs	The default format for timestamps in JSON and RESTful APIs
Programming	Modern languages have bult-in support like toISOString()

The RFC 9557 Format

RFC 9557 is the primary format used by JavaScript Temporal to represent dates.

Feature	ISO 8601	RFC 3339	RFC 9557
Format	YYYY-MM-DDThh:mm:ssZ	Same	Same
UTC Offset	Yes	Yes	Yes
IANA Zone	No	No	[America/New_York]
Calendars	ISO only	ISO only	[u-ca=hebrew]
Compabile	The Standard	Subset of ISO 8601	Extends 3339

RFC 9557 was created because ISO 8601 and RFC 3339 did not contain enough > information to determine the geographical time zone or handle future DST > (Daylight Saving Time) changes.

RFC 5545 iCalendar

RFC 5545 is the official internet standard for the iCalendar data format. It defines how calendar systems should store and share calendar data like meetings, tasks, and free/busy times using plain text files.

iCalendar is text-based. It Uses readable lines of text encoded in UTF-8.

iCalendar is is application independent. It works across different apps like Apple Calendar, Google Calendar, and Microsoft Outlook.

Examples

Example Code

javascript

Try it Yourself

BEGIN:VCALENDAR

VERSION:2.0

PRODID:-//Example Corp//NONSGML Calendar App//EN

CALSCALE:GREGORIAN

METHOD:PUBLISH

BEGIN:VEVENT

UID:uid123456789@example.com

DTSTAMP:20260810T120000Z

ORGANIZER;CN=John Doe:mailto:john.doe@example.com

DTSTART:20260812T140000Z

DTEND:20260812T150000Z

SUMMARY:Project Kickoff Meeting

DESCRIPTION:Initial team synchronization and roadmap review.

LOCATION:Conference Room A

STATUS:CONFIRMED

CLASS:PUBLIC

END:VEVENT

END:VCALENDAR

Field	Description
BEGIN:VCALENDAR	Required. Begins a calendar object.
VERSION:2.0	Required. Specifies compliance with RFC 5545.
PRODID	Required. -//Organization//Product//Language.
BEGIN:VEVENT	Required. Begins a single calendar event.
UID	A globally unique event identifier to prevent duplicates.
DTSTAMP	The exact date and time the file was generated.
ORGANIZER	Defines who is hosting or managing the event.
DTSTART	Event start time (YYYYMMDDTHHMMSSZ in UTC).
DTEND	Event end time (YYYYMMDDTHHMMSSZ in UTC).
SUMMARY	The title of the calendar event.
DESCRIPTION	The detailed notes or body text of the event.
LOCATION	The location of the event.
CLASS	PUBLIC, PRIVATE or CONFIDENTIAL.
STATUS	TENTATIVE, CONFIRMED or CANCELLED.
END:VEVENT	Required. Ends a single calendar event.
END:VCALENDAR	Required. Ends a calendar object.

Calendar Systems in JavaScript

Temporal supports multiple calendar systems
The calendars are based on the Unicode CLDR standard
They are used with the Intl API.
The default is iso8601.
Calendars affect how dates are interpreted and displayed.
Use [u-ca=calendar] to specify a calendar.

Supported Calendar Identifiers

Calendar ID	Name	Region	Description
iso8601	ISO 8601	Worldwide	The default calendar used by Temporal
gregory	Gregorian	Worldwide	The most widely used civil calendar today
buddhist	Buddhist	Thailand	A different year numbering system than Gregorian
chinese	Chinese	China	A lunisolar calendar used for traditional festivals
coptic	Coptic	Egypt	Used by the Coptic Orthodox Church
dangi	Dangi	Korea	Traditional Korean lunisolar calendar
ethiopic	Ethiopic	Ethiopia	A calendar with 13 months
ethioaa	Ethiopic AA	Ethiopia	Alternative Ethiopic era
hebrew	Hebrew	Israel	A lunisolar calendar used in Jewish traditions
indian	Indian (Saka)	India	The official civil calendar of India
islamic	Islamic	Middle East	A lunar calendar used in Islamic countries
islamic-umalqura	Umm al-Qura	Saudi Arabia	The official Saudi calendar
japanese	Japanese	Japan	Based on imperial eras
persian	Persian	Iran	A solar calendar with high accuracy
roc	Republic of China	Taiwan	Used in Taiwan (Minguo calendar)

Calendar Systems Explained

A calendar system defines how dates are calculated.

Different cultures use different calendars.

Solar Calendars

Based on the Earth's orbit around the sun.

Gregorian
ISO 8601
Persian

These calendars track seasons accurately.

Lunar Calendars

Based on the phases of the moon.

Islamic

Lunar calendars have shorter years.

Lunisolar Calendars

Combine solar and lunar cycles.

Chinese
Hebrew
Dangi

They adjust months to stay aligned with seasons.

Era-Based Calendars

Use eras instead of a continuous year count.

Japanese
ROC (Taiwan)

Using Calendars in Temporal

JavaScript syntax and algorithm demonstration.

Temporal.PlainDate.from("2026-05-17[u-ca=japanese]")

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