Iran Standard Time

{{Short description|Identifier for a time offset from UTC of +03:30}}

Iran Standard Time (IRST) or Iran Time (IT) is the time zone used in Iran. Iran uses a UTC offset UTC+03:30. IRST is defined by the 52.5 degrees east meridian, 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 (DST) (called Iran Daylight Time or IRDT).{{cite web|url=http://timeanddate.com/worldclock/timezone.html?n=246 |title=Time zone and daylight saving time for Iran – Tehran between 2010 and 2019 |publisher=Timeanddate.com |access-date=9 May 2010}} It was reintroduced from 21 March 2008. On 21 September 2022, Iran abolished DST and now observes standard time year-round.{{cite web|url=https://www.timeanddate.com/news/time/iran-dst-2022.html|title=Iran Considers Abolishing DST|website=timeanddate.com|date=|accessdate=13 May 2022}}{{cite web|url=https://livingintehran.com/2022/09/21/daylight-saving-time-ends-in-iran/|date=2022-09-21|title=Daylight Saving Time Ends in Iran|website=Livingintehran.com}}

Daylight Saving Time transitions

The dates of DST transitions in Iran were based on the Solar Hijri calendar, the official calendar of Iran, which is in turn based on the March equinox (Nowruz) as determined by astronomical calculation at the meridian 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, 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{{Cite web|title = Culture of Iran: No-Rooz, The Iranian New Year at Present Times|url = http://www.iranchamber.com/culture/articles/norooz_iranian_new_year.php|website = www.iranchamber.com|access-date = 1 February 2016}} 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).{{cite web |url=https://mm.icann.org/pipermail/tz/2003-March/012052.html |title=Iran daylight saving time correction |author=Roozbeh Pournader |date=15 March 2003 |access-date=1 December 2018}}{{cite web |url=https://github.com/eggert/tz/blob/d053d36c480fcf2fe6d37636da9eff1b8eddca70/asia#L1278-L1299 |title=asia file, lines 1278–1299 |author=tz database |website=GitHub |author-link=tz database |date=30 November 2018 |access-date=1 December 2018}}