Iran Standard Time
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). It was reintroduced from 21 March 2008. On 21 September 2022, Iran abolished DST for the second time and now observes standard time year-round.
01Daylight 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 did not 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 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).
02Time 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) |
Sources and credits
This article is adapted from the Wikipedia article “Iran Standard Time”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.
Images, from Wikimedia Commons:
- Time Zones of the Middle East.svg by Cyfraw, CC BY-SA 4.0
- Shahr Rey, Iran 2013 (10) (15002619346).jpg by Dr. Nasser Haghighat, CC BY 2.0
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