Iran Standard Time (IRST) or Iran Time (IT) is the

time zone A time zone is an area which observes a uniform standard time for legal, commercial and social purposes. Time zones tend to follow the boundaries between countries and their subdivisions instead of strictly following longitude, because i ...

used in

Iran Iran, officially the Islamic Republic of Iran, and also called Persia, is a country located in Western Asia. It is bordered by Iraq and Turkey to the west, by Azerbaijan and Armenia to the northwest, by the Caspian Sea and Turkm ...

. Iran uses a UTC offset UTC+03:30. IRST is defined by the 52.5 degrees east

meridian Meridian or a meridian line (from Latin ''meridies'' via Old French ''meridiane'', meaning “midday”) may refer to Science * Meridian (astronomy), imaginary circle in a plane perpendicular to the planes of the celestial equator and horizon * ...

, the same meridian which defines the Iranian calendar and is the official meridian of Iran. Between 2005 and 2008, by decree of President Mahmoud Ahmadinejad, Iran did not observe

daylight saving time Daylight saving time (DST), also referred to as daylight savings time or simply daylight time (United States, Canada, and Australia), and summer time (United Kingdom, European Union, and others), is the practice of advancing clocks (typical ...

(DST) (called ''Iran Daylight Time'' or ''IRDT''). It was reintroduced from 21 March 2008. On 21 September 2022, Iran abolished DST and now observes standard time year-round.

Daylight Saving Time transitions

The dates of DST transitions in Iran were based on the

Solar Hijri calendar The Solar calendar ( fa, گاه‌شماری هجری خورشیدی, Gâhšomâri-ye Xoršidi; ps, لمريز لېږدیز کلیز, lamrez legdez kalhandara; ku, ڕۆژژمێری کۆچیی ھەتاوی, Salnameya Koçberiyê) is a solar c ...

, the official calendar of

, which is in turn based on the

March equinox The March equinox or northward equinox is the equinox on the Earth when the subsolar point appears to leave the Southern Hemisphere and cross the celestial equator, heading northward as seen from Earth. The March equinox is known as the vern ...

( Nowruz) as determined by astronomical calculation at the

for Iran Standard Time (52.5°E or GMT+3.5h). This resulted in the unique situation wherein the dates of DST transitions didn't fall on the same weekday each year as they do in most other countries. DST started in Iran at 24:00 on 1 Farvardin, which corresponds to either 20 or 21 March in the

Gregorian calendar The Gregorian calendar is the calendar used in most parts of the world. It was introduced in October 1582 by Pope Gregory XIII as a modification of, and replacement for, the Julian calendar. The principal change was to space leap years di ...

, depending on the precise timing of the equinox. (This is equivalent to 00:00 on 2 Farvardin, either 21 or 22 March.) Clocks moved forward at that time to 01:00 on 2 Farvardin (21 or 22 March). This spring change took place at the end of the day of Nowruz, which is the Iranian

New Year's Day New Year's Day is a festival observed in most of the world on 1 January, the first day of the year in the modern Gregorian calendar. 1 January is also New Year's Day on the Julian calendar, but this is not the same day as the Gregorian one. Wh ...

and the most important festival in Iranian culture. DST likewise ended in Iran at 24:00 on 30 Shahrivar, which corresponds to either 20 or 21 September. (Equivalently, at 00:00 on 31 Shahrivar, either 21 or 22 September). Clocks moved backward to 23:00 on 30 Shahrivar (20 or 21 September).

Recent and upcoming dates

Time zone changes

IANA time zone database

The

IANA time zone database The tz database is a collaborative compilation of information about the world's time zones, primarily intended for use with computer programs and operating systems. Paul Eggert is its current editor and maintainer, with the organizational back ...

contains one zone for Iran in the file

zone.tab This is a list of time zones from release of the tz database. Legend Type * Canonical - The primary, preferred zone name. * Link - An alternative name (alias) which links to a canonical zone. * Link - A standard Link (as above). The dagger symb ...

, named Asia/Tehran.

References

Time in Iran Time zones {{iran-stub

Daylight Saving Time transitions

Recent and upcoming dates

Time zone changes

IANA time zone database

See also

References