Convert IRST to MST
MST is 10 hours 30 minutes behind IRST. IRST is UTC+3:30 and MST is UTC−7.
Right now: IRST · MST
Best time to schedule a meeting
Standard 9–5 working hours do not overlap at all between IRST and MST. Someone has to take an early or late call — or use asynchronous communication instead.
| IRST | MST | Suitable? |
|---|---|---|
| 9:00 AM | 10:30 PM (previous day) | outside 9–5 |
| 10:00 AM | 11:30 PM (previous day) | outside 9–5 |
| 11:00 AM | 12:30 AM | outside 9–5 |
| 12:00 PM | 1:30 AM | outside 9–5 |
| 1:00 PM | 2:30 AM | outside 9–5 |
| 2:00 PM | 3:30 AM | outside 9–5 |
| 3:00 PM | 4:30 AM | outside 9–5 |
| 4:00 PM | 5:30 AM | outside 9–5 |
| 5:00 PM | 6:30 AM | outside 9–5 |
IRST to MST conversion table
| IRST | MST |
|---|---|
| 12:00 AM | 1:30 PM (previous day) |
| 1:00 AM | 2:30 PM (previous day) |
| 2:00 AM | 3:30 PM (previous day) |
| 3:00 AM | 4:30 PM (previous day) |
| 4:00 AM | 5:30 PM (previous day) |
| 5:00 AM | 6:30 PM (previous day) |
| 6:00 AM | 7:30 PM (previous day) |
| 7:00 AM | 8:30 PM (previous day) |
| 8:00 AM | 9:30 PM (previous day) |
| 9:00 AM | 10:30 PM (previous day) |
| 10:00 AM | 11:30 PM (previous day) |
| 11:00 AM | 12:30 AM |
| 12:00 PM | 1:30 AM |
| 1:00 PM | 2:30 AM |
| 2:00 PM | 3:30 AM |
| 3:00 PM | 4:30 AM |
| 4:00 PM | 5:30 AM |
| 5:00 PM | 6:30 AM |
| 6:00 PM | 7:30 AM |
| 7:00 PM | 8:30 AM |
| 8:00 PM | 9:30 AM |
| 9:00 PM | 10:30 AM |
| 10:00 PM | 11:30 AM |
| 11:00 PM | 12:30 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 MST
Mountain Standard Time (MST) is UTC−7. It is used in Denver and Salt Lake City in winter, and Phoenix all year.
Mountain Standard Time is UTC−7. Denver and Salt Lake City use it in winter and switch to MDT in summer; Arizona does not switch at all and stays on MST year-round, which means Phoenix agrees with Denver in winter and with Los Angeles in summer. The Navajo Nation, inside Arizona, does observe daylight saving, so the state contains both. Any scheduling system that maps "Arizona" to "Mountain Time" without the no-DST flag will be an hour out for eight months.
Does this gap change with the seasons?
This gap is seasonal. The abbreviations themselves are fixed offsets, but the region on MST switches to MDT (UTC−6) from March to November. So the 10.5-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 MST?
9:00 AM IRST is 10:30 PM MST (previous day).
Is MST ahead of IRST?
MST is 10 hours 30 minutes behind IRST.
Which time zone does this use?
IRST is UTC+3:30 and MST is UTC−7. 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.