Convert MDT to IRST
IRST is 9 hours 30 minutes ahead of MDT. MDT is UTC−6 and IRST is UTC+3:30.
Right now: MDT · IRST
Best time to schedule a meeting
Standard 9–5 working hours do not overlap at all between MDT and IRST. Someone has to take an early or late call — or use asynchronous communication instead.
| MDT | IRST | Suitable? |
|---|---|---|
| 9:00 AM | 6:30 PM | outside 9–5 |
| 10:00 AM | 7:30 PM | outside 9–5 |
| 11:00 AM | 8:30 PM | outside 9–5 |
| 12:00 PM | 9:30 PM | outside 9–5 |
| 1:00 PM | 10:30 PM | outside 9–5 |
| 2:00 PM | 11:30 PM | outside 9–5 |
| 3:00 PM | 12:30 AM (next day) | outside 9–5 |
| 4:00 PM | 1:30 AM (next day) | outside 9–5 |
| 5:00 PM | 2:30 AM (next day) | outside 9–5 |
MDT to IRST conversion table
| MDT | IRST |
|---|---|
| 12:00 AM | 9:30 AM |
| 1:00 AM | 10:30 AM |
| 2:00 AM | 11:30 AM |
| 3:00 AM | 12:30 PM |
| 4:00 AM | 1:30 PM |
| 5:00 AM | 2:30 PM |
| 6:00 AM | 3:30 PM |
| 7:00 AM | 4:30 PM |
| 8:00 AM | 5:30 PM |
| 9:00 AM | 6:30 PM |
| 10:00 AM | 7:30 PM |
| 11:00 AM | 8:30 PM |
| 12:00 PM | 9:30 PM |
| 1:00 PM | 10:30 PM |
| 2:00 PM | 11:30 PM |
| 3:00 PM | 12:30 AM (next day) |
| 4:00 PM | 1:30 AM (next day) |
| 5:00 PM | 2:30 AM (next day) |
| 6:00 PM | 3:30 AM (next day) |
| 7:00 PM | 4:30 AM (next day) |
| 8:00 PM | 5:30 AM (next day) |
| 9:00 PM | 6:30 AM (next day) |
| 10:00 PM | 7:30 AM (next day) |
| 11:00 PM | 8:30 AM (next day) |
About MDT
Mountain Daylight Time (MDT) is UTC−6. It is used in Denver and Salt Lake City from March to November.
Mountain Daylight Time is UTC−6, the summer clock for Denver and Salt Lake City. During those months it coincides with Central Standard Time, which is a genuine source of confusion in a country that spans both: a meeting at "6pm MDT" and one at "6pm CST" are the same instant, but the second is not a time anyone is actually on in summer.
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.
Does this gap change with the seasons?
This gap is seasonal. The abbreviations themselves are fixed offsets, but the region on MDT switches to MST (UTC−7) from November to March. So the 9.5-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 MDT in IRST?
9:00 AM MDT is 6:30 PM IRST.
Is IRST ahead of MDT?
IRST is 9 hours 30 minutes ahead of MDT.
Which time zone does this use?
MDT is UTC−6 and IRST is UTC+3:30. 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.