| UTC+02:00 UTC+03:00 | Eastern European Time / Eastern European Summer Time | |
| UTC+03:00 | Arabia Standard Time / Turkey Time | |
| UTC+03:30 | Iran Standard Time | |
| UTC+04:00 | Gulf Standard Time |
Iran Standard Time (IRST) orIran Time (IT) is thetime zone used in Iran. Iran uses a UTC offsetUTC+03:30. IRST is defined by the 52.5 degrees eastmeridian, the same meridian which defines theIranian calendar and is the official meridian of Iran.
Between 2005 and 2008, by decree of PresidentMahmoud Ahmadinejad, Iran did not observedaylight saving time (DST) (calledIran Daylight Time orIRDT).[1] It was reintroduced from 21 March 2008. On 21 September 2022, Iran abolished DST and now observes standard time year-round.[2][3]
The dates of DST transitions in Iran were based on theSolar Hijri calendar, the official calendar ofIran, which is in turn based on theMarch equinox (Nowruz) as determined by astronomical calculation at themeridian for Iran Standard Time (52.5°E or GMT+3.5h). This resulted in the unique situation wherein the dates of DST transitions did not fall on the same weekday each year as they do in most other countries.
DST started in Iran at 24:00 on 1Farvardin, which corresponds to either 20 or 21 March in theGregorian 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 ofNowruz, which is theIranianNew Year's Day[4] and the most important festival in Iranian culture.
DST likewise ended in Iran at 24:00 on 30Shahrivar, 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]
| 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) |
asia file, lines 1278–1299".GitHub. Retrieved1 December 2018.
