Iran Standard Time

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.

Time in the Middle East
    UTC+02:00 Egypt Standard Time
    UTC+02:00

UTC+03:00		 Eastern European Time /
Israel Standard Time /
Palestine Standard Time
Eastern European Summer Time /
Israel Summer Time /
Palestine Summer Time
    UTC+03:00 Arabia Standard Time /
Turkey Time
    UTC+03:30 Iran Standard Time
    UTC+04:00 Persian Gulf Standard Time
▉▉▉▉ Standard time observed all year
▉ Daylight saving time observed

Between 2005 and 2008, by decree of President Mahmoud Ahmadinejad, Iran did not observe daylight saving time (DST) (called Iran Daylight Time or IRDT).[1] It was reintroduced from 21 March 2008. On 21 September 2022, Iran abolished DST and now observes standard time year-round.[2][3]

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[4] 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).[5][6]

Recent and upcoming dates
Year[7] DST Start DST End
2017 Wed, Mar 22, 00:00 Fri, Sep 22, 00:00
2018 Thu, Mar 22, 00:00 Sat, Sep 22, 00:00
2019 Fri, Mar 22, 00:00 Sun, Sep 22, 00:00
2020 Sat, Mar 21, 00:00 Mon, Sep 21, 00:00
2021 Mon, Mar 22, 00:00 Wed, Sep 22, 00:00
2022 Tue, Mar 22, 00:00 Thu, Sep 22, 00:00

Time zone changes
Period in use Time offset from GMT Name of time
before 1945 UTC+03:25:44 Tehran Mean Time (TMT)
1946 – 1977 UTC+03:30 Iran Standard Time (IRST)
1977 – 1978 UTC+04:00
UTC+05:00		 Iran Standard Time (IRST)
Iran Daylight Time (IRDT)
1979 – 1980 UTC+03:30
UTC+04:30		 Iran Standard Time (IRST)
Iran Daylight Time (IRDT)
1981 – 1990 UTC+03:30 Iran Standard Time (IRST)
1991 – 2005 UTC+03:30
UTC+04:30		 Iran Standard Time (IRST)
Iran Daylight Time (IRDT)
2006 – 2007 UTC+03:30 Iran Standard Time (IRST)
2008 – 2022 UTC+03:30
UTC+04:30		 Iran Standard Time (IRST)
Iran Daylight Time (IRDT)
2022 – present UTC+03:30 Iran Standard Time (IRST)

IANA time zone database

The IANA time zone database contains one zone for Iran in the file zone.tab, named Asia/Tehran.

See also

References
  1. "Time zone and daylight saving time for Iran – Tehran between 2010 and 2019". Timeanddate.com. Retrieved 9 May 2010.
  2. "Iran Considers Abolishing DST". timeanddate.com. Retrieved 13 May 2022.
  3. "Daylight Saving Time Ends in Iran". Livingintehran.com. 2022-09-21.
  4. "Culture of Iran: No-Rooz, The Iranian New Year at Present Times". www.iranchamber.com. Retrieved 1 February 2016.
  5. Roozbeh Pournader (15 March 2003). "Iran daylight saving time correction". Retrieved 1 December 2018.
  6. tz database (30 November 2018). "asia file, lines 1278–1299". GitHub. Retrieved 1 December 2018.
  7. "Time Changes in Tehran over the years".
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