Convert IRST to GMT
GMT is 3 hours 30 minutes behind IRST. IRST is UTC+3:30 and GMT is UTC+0.
Right now: IRST · GMT
Best time to schedule a meeting
Standard 9–5 working hours overlap for 4 hours: 1:00 PM–5:00 PM IRST (9:00 AM–1:00 PM GMT). Schedule meetings inside that window.
| IRST | GMT | Suitable? |
|---|---|---|
| 9:00 AM | 5:30 AM | outside 9–5 |
| 10:00 AM | 6:30 AM | outside 9–5 |
| 11:00 AM | 7:30 AM | outside 9–5 |
| 12:00 PM | 8:30 AM | outside 9–5 |
| 1:00 PM | 9:30 AM | working hours |
| 2:00 PM | 10:30 AM | working hours |
| 3:00 PM | 11:30 AM | working hours |
| 4:00 PM | 12:30 PM | working hours |
| 5:00 PM | 1:30 PM | working hours |
IRST to GMT conversion table
| IRST | GMT |
|---|---|
| 12:00 AM | 8:30 PM (previous day) |
| 1:00 AM | 9:30 PM (previous day) |
| 2:00 AM | 10:30 PM (previous day) |
| 3:00 AM | 11:30 PM (previous day) |
| 4:00 AM | 12:30 AM |
| 5:00 AM | 1:30 AM |
| 6:00 AM | 2:30 AM |
| 7:00 AM | 3:30 AM |
| 8:00 AM | 4:30 AM |
| 9:00 AM | 5:30 AM |
| 10:00 AM | 6:30 AM |
| 11:00 AM | 7:30 AM |
| 12:00 PM | 8:30 AM |
| 1:00 PM | 9:30 AM |
| 2:00 PM | 10:30 AM |
| 3:00 PM | 11:30 AM |
| 4:00 PM | 12:30 PM |
| 5:00 PM | 1:30 PM |
| 6:00 PM | 2:30 PM |
| 7:00 PM | 3:30 PM |
| 8:00 PM | 4:30 PM |
| 9:00 PM | 5:30 PM |
| 10:00 PM | 6:30 PM |
| 11:00 PM | 7:30 PM |
About IRST
Iran Standard Time (IRST) is UTC+3:30. It is used in Iran, all year.
Iran Standard Time is UTC+3:30. Iran ran daylight saving for decades and stopped in 2022, so material written before then puts the country half an hour further ahead in summer and is now wrong. Half-hour offsets are rare enough that scheduling tools sometimes round them, which turns a correct calculation into a thirty-minute error.
About GMT
Greenwich Mean Time (GMT) is UTC+0. It is used in the UK and Ireland in winter, Portugal, Iceland and much of West Africa.
The trap with GMT is that the United Kingdom is not on it for most of the year. From late March to late October the UK runs BST, UTC+1, so a meeting agreed "10am GMT" with a London colleague in July is an hour out unless both parties meant the abbreviation literally. Broadcasters and airlines avoid the ambiguity by saying UTC. GMT itself is fixed at UTC+0 and does not shift; it is the UK's clocks that move away from it and back.
Does this gap change with the seasons?
This gap is seasonal. The abbreviations themselves are fixed offsets, but the region on GMT switches to BST (UTC+1) from late March to late October. So the 3.5-hour figure on this page is correct for the part of the year when both places are actually on these abbreviations, and changes by an hour outside it.
IRST does not shift, so the whole change comes from one side. A recurring meeting fixed in IRST will appear to move by an hour for everyone on the other side, twice a year, without anyone changing anything.
This is the reason scheduling systems store an IANA zone such as Region/City rather than an offset or an abbreviation: the zone knows its own rules and the offset does not.
Frequently asked questions
What time is 9:00 AM IRST in GMT?
9:00 AM IRST is 5:30 AM GMT.
Is GMT ahead of IRST?
GMT is 3 hours 30 minutes behind IRST.
Which time zone does this use?
IRST is UTC+3:30 and GMT is UTC+0. Both abbreviations denote a single fixed offset, so this conversion never shifts with daylight saving — what changes is which abbreviation a place is using at the time.