GMT to IRST Converter
The United Kingdom is on summer time: BST (UTC+1) until Sun, Oct 25.
Iceland and Ghana stay on GMT (UTC+0).
Start by searching for a time zone, city, or town.
Add one or more places to compare local times, adjust the date, and share the result.
Quick answers
Selected conversion
12:00 pm12:00 GMT (UTC+0), Oct 12, 2026 = 3:30 pm15:30 IRST (UTC+3:30), Oct 12, 2026
GMT is 3 hours and 30 minutes behind IRST.
GMT and IRST examples
These examples always use GMT (UTC+0) and IRST (UTC+3:30). They stay the same when you change the date or time above. The selected conversion may differ when daylight saving time applies.
GMT is 3 hours and 30 minutes behind IRST.
How the time difference changes
GMT is 3 hours and 30 minutes behind IRST year-round.
Working hours of 9:00 am to 5:00 pm in GMT correspond to 12:30 pm to 8:30 pm in IRST.Working hours of 09:00 to 17:00 in GMT correspond to 12:30 to 20:30 in IRST.
Compare GMT time with IRST time, including current local time, UTC offsets, time difference, daylight saving changes, working hours, and shareable meeting times.
Time Difference
Greenwich Mean Time is 3 hours and 30 minutes behind Iran Standard Time.
12:00 pm12:00 in GMT is 3:30 pm15:30 in IRST
GMT to IRST call time
Best time for a conference call or a meeting is between 9am-1:30pm09:00-13:30 in GMT which corresponds to 12:30pm-5pm12:30-17:00 in IRST
12:00 pm12:00 Greenwich Mean Time (GMT). Offset UTC 0:00 hours
3:30 pm15:30 Iran Standard Time (IRST). Offset UTC +3:30 hours
12:00 pm12:00 GMT / 3:30 pm15:30 IRST
Choose an hour to update the converter. Day labels such as “next day” or “+1” are relative to the selected date in the first column. Use Up and Down arrow keys, Home or End to move between hours, then Enter or Space to select.
| GMT | IRST |
|---|---|
| 3:30am | |
| 4:30am | |
| 5:30am | |
| 6:30am | |
| 7:30am | |
| 8:30am | |
| 9:30am | |
| 10:30am | |
| 11:30am | |
| 12:30pm | |
| 1:30pm | |
| 2:30pm | |
| 3:30pm | |
| 4:30pm | |
| 5:30pm | |
| 6:30pm | |
| 7:30pm | |
| 8:30pm | |
| 9:30pm | |
| 10:30pm | |
| 11:30pm | |
| 12:30am next day | |
| 1:30am next day | |
| 2:30am next day | |
| 03:30 | |
| 04:30 | |
| 05:30 | |
| 06:30 | |
| 07:30 | |
| 08:30 | |
| 09:30 | |
| 10:30 | |
| 11:30 | |
| 12:30 | |
| 13:30 | |
| 14:30 | |
| 15:30 | |
| 16:30 | |
| 17:30 | |
| 18:30 | |
| 19:30 | |
| 20:30 | |
| 21:30 | |
| 22:30 | |
| 23:30 | |
| 00:30 next day | |
| 01:30 next day | |
| 02:30 next day |
Greenwich Mean Time
Offset: GMT is the same as Greenwich Mean Time (GMT).
Countries using this time zone: Burkina Faso, Côte d'Ivoire, Britain (UK), Guernsey, Ghana, Greenland, Gambia, Guinea, Guinea-Bissau, Ireland, Isle of Man, Iceland, Jersey, Liberia, Mali, Mauritania, St Helena, Sierra Leone, Senegal, Sao Tome & Principe, Togo
Principal Cities: The largest city in the GMT time zone is London in the United Kingdom, with about 8.962 million people. Other major cities in this time zone include Abidjan, Bamako, Dakar, Kumasi.
Greenwich Mean Time (GMT) originally referred to the mean solar time at the Royal Observatory in Greenwich, London. It is now often used to refer to Coordinated Universal Time (UTC) when this is viewed as a time zone, and in casual use the two are the same. In the military, GMT is known as Zulu time. Greenwich Mean Time was the same as Universal Time (UT), a standard astronomical concept used in many technical fields, until the introduction of UTC in 1972.
Today the lighter areas are on UTC+1 (British Summer Time, Irish Standard Time).
GMT representations, usage and related time zones
- Z - is the zone designator for the zero UTC/GMT offset, also known as 'Zulu' time
- +00 - basic short
- +0000 - basic
- +00:00 - extended
- +0000 - sign character (+) followed by a four digit time providing hours (00) and minutes (00) of the offset. Indicates the zero UTC/GMT offset.
- Zulu - Military abbreviation for GMT
- Z - short form of 'Zulu'
- Africa/Abidjan
- Africa/Accra
- Africa/Bamako
- Africa/Banjul
- Africa/Bissau
- Africa/Conakry
- Africa/Dakar
- Africa/Freetown
- Africa/Lome
- Africa/Monrovia
- Africa/Nouakchott
- Africa/Ouagadougou
- Africa/Sao_Tome
- Africa/Timbuktu
- America/Danmarkshavn
- Atlantic/Reykjavik
- Atlantic/St_Helena
- Eire
- Etc/GMT
- Etc/GMT+0
- Etc/GMT-0
- Etc/GMT0
- Etc/Greenwich
- Europe/Belfast
- Europe/Dublin
- Europe/Guernsey
- Europe/Isle_of_Man
- Europe/Jersey
- Europe/London
- GB
- GB-Eire
- GMT
- GMT+0
- GMT-0
- GMT0
- Greenwich
- Iceland
- EGST - Eastern Greenland Summer Time
- GMT - Greenwich Mean Time
- WET - Western European Time
- AZOST - Azores Summer Time
- UTC - Coordinated Universal Time
- WT - Western Sahara Standard Time
- Z - Zulu Time Zone
Iran Standard Time
Offset: IRST is 3 hours and 30 minutes ahead of Greenwich Mean Time (GMT).
Countries using this time zone: Iran
Principal Cities: The largest city in the IRST time zone is Tehran in Iran, with about 7.153 million people. Other major cities in this time zone include Mashhad, Isfahan, Karaj, Tabriz.
Daylight Saving: Clocks in Iran Standard Time (IRST) do not change for daylight saving time, so IRST stays the same throughout the year. Other time zones may set clocks forward in summer and back in winter; see upcoming clock changes worldwide.
IRST representations, usage and related time zones
- +0330 - basic
- +03:30 - extended
- +0330 - sign character (+) followed by a four digit time providing hours (03) and minutes (30) of the offset. Indicates an offset of three hours and thirty minutes to the east of the zero meridian.