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 (called Iran Daylight Time or IRDT).[1][2] It was reintroduced from 21 March 2008.

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Daylight Saving Time transitionsEdit

The dates of DST transitions in Iran are 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 results in the unusual situation wherein the dates of DST transitions don't fall on the same weekday each year as they do in most other countries.

DST starts 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 move forward at that time to 01:00 on 2 Farvardin (21 or 22 March). This spring change takes place at the end of the day of Nowruz, which is the Iranian New Year's Day[3] and the most important festival in Iranian culture.

DST likewise ends 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 move backward to 23:00 on 30 Shahrivar (20 or 21 September).[4][5]

Recent and upcoming datesEdit

Year[6] 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
2023 Wed, Mar 22, 00:00 Fri, Sep 22, 00:00

Time zone changesEdit

Period in use Time offset from GMT Name of Time
1800 – 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 – present UTC+03:30
UTC+04:30
Iran Standard Time (IRST)
Iran Daylight Time (IRDT)

IANA time zone databaseEdit

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

See alsoEdit

ReferencesEdit

  1. ^ "Iran will not observe DST". Presstv.ir. 20 March 2007. Retrieved 9 May 2010.
  2. ^ "Time zone and daylight saving time for Iran – Tehran between 2010 and 2019". Timeanddate.com. Retrieved 9 May 2010.
  3. ^ "Culture of Iran: No-Rooz, The Iranian New Year at Present Times". www.iranchamber.com. Retrieved 1 February 2016.
  4. ^ Roozbeh Pournader (15 March 2003). "Iran daylight saving time correction". Retrieved 1 December 2018.
  5. ^ tz database (30 November 2018). "asia file, lines 1278–1299". Retrieved 1 December 2018.
  6. ^ "Time Changes in Tehran over the years".