IRST to MST
-10h 30mIRST
IRSTSOURCEMST
MSTGreen rows indicate typical business hours (9 AM - 5 PM)
IRST and MST on the World Map
The map below highlights the IRST (Iran Standard Time) and MST (Mountain Standard Time) timezone regions across the globe.
IRST – Iran Standard Time
UTC+03:30Iran Standard Time (IRST) is the time zone for Iran, 3 hours and 30 minutes ahead of UTC.
- •IRST is one of only a few time zones with a 30-minute offset.
- •Iran observes daylight saving time, switching to IRDT (UTC+04:30).
- •Tehran has a metropolitan population of over 16 million.
MST – Mountain Standard Time
UTC-07:00Mountain Standard Time (MST) is the time zone for the Mountain region of North America, 7 hours behind UTC.
- •Arizona does not observe daylight saving time, staying on MST year-round.
- •The Navajo Nation in Arizona does observe DST, unlike the rest of the state.
- •Denver, the 'Mile High City', is the largest city fully in MST.
- •MST covers 6 US states entirely and parts of several others.
Time Conversion Guide: IRST to MST
IRST runs on Iran Standard Time (IRST) at UTC+03:30. MST runs on Mountain Standard Time (MST) at UTC-07:00. That puts IRST 10 hours 30 minutes behind MST — a difference of -10h 30m at the current offsets.
In practice, when it is 9:00 AM in IRST it is 10:30 PM in MST on the previous day. Midnight in IRST is 1:30 PM in MST. Neither zone observes daylight saving time, so the offset between them stays constant all year.
IRST to MST time conversion table
| IRST (IRST) | MST (MST) | Day |
|---|---|---|
| 12:00 AM | 1:30 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 |
| 12:00 PM | 1:30 AM | same day |
| 3:00 PM | 4:30 AM | same day |
| 5:00 PM | 6:30 AM | same day |
| 6:00 PM | 7:30 AM | same day |
| 9:00 PM | 10:30 AM | same day |
Why people convert IRST to MST time
- Scheduling a call from IRST to MST: a 10:00 AM start in IRST lands at 11:30 PM in MST the previous day, so you can confirm the slot without doing the arithmetic yourself.
- Handling a -10h 30m gap: IRST and MST have no overlap inside a normal 9-to-5 day, so real-time meetings need an early-morning or late-evening slot on one side. 9:00 AM in MST is 10:30 PM in IRST.
- Keeping family and friends in sync: knowing that 8:00 PM in IRST is 9:30 AM in MST makes it easy to avoid calling at 3 AM.
- Always state the zone abbreviation, not just the hour. "3:00 PM IRST" is unambiguous; "3 PM" across a -10h 30m gap is not.
- With a -10h 30m gap there is no shared 9-to-5 window, so alternate the early start: one week IRST takes the early slot, the next week MST does.
About IRST (Iran Standard Time)
Iran Standard Time (IRST) is one of the few time zones with a 30-minute offset. Iran observes daylight saving time (IRDT, UTC+04:30) from late March to late September. Tehran, the capital, is one of the largest cities in the Middle East.
About MST (Mountain Standard Time)
Mountain Standard Time (MST) covers the Rocky Mountain region of the United States and Canada. Arizona is notable for not observing daylight saving time, staying on MST year-round (except the Navajo Nation). The time zone includes major cities like Denver, Phoenix, Calgary, and Salt Lake City. During summer, most areas switch to Mountain Daylight Time (MDT, UTC-06:00).
Best time to call between IRST and MST
With a -10h 30m offset there is no overlap inside a normal 9 AM – 5 PM day. MST opens at 9:00 AM MST, which is 10:30 PM in IRST, so real-time calls need an early-morning or late-evening slot on one side.
Business hours overlap
IRST and MST have no shared working hours because of the -10h 30m gap. Teams need to alternate early starts or rely on asynchronous handovers.
IRST is 10 hours 30 minutes behind MST (IRST UTC+03:30 → MST UTC-07:00). There is no shared 9-to-5 window, so plan around an early or late slot. Remember to re-check around daylight-saving transitions.
🕐 Daylight Saving Time Info
IRST
Does not observe DST
MST
☀ Currently in DST
Standard: UTC-07:00 · DST: UTC-06:00
Clocks fall back on Sun, Nov 1, 2026
Learn More About Time
Dive deeper into the fascinating world of timekeeping, time zones, and how they shape our global society:
Frequently Asked Questions
What is the time difference between IRST and MST?
IRST (IRST, UTC+03:30) is 10 hours 30 minutes behind MST (MST, UTC-07:00). The gap is currently -10h 30m.
How do I convert IRST time to MST time?
Add -10h 30m to IRST local time. For example, 9:00 AM in IRST is 10:30 PM in MST (previous day).
What time is it in MST right now?
MST uses MST at UTC-07:00. Use the live converter at the top of this page — it updates in real time and already accounts for the -10h 30m offset from IRST.
What is the best time to call MST from IRST?
There is no shared working-hours window because of the -10h 30m gap. The closest option is 1:00 PM in IRST, which is 2:30 AM in MST.
Which is behind, IRST or MST?
IRST is 10 hours 30 minutes behind MST. When it is 12:00 PM in IRST it is 1:30 AM in MST.
Does daylight saving time affect the IRST–MST difference?
Neither zone observes daylight saving time, so the -10h 30m offset between IRST and MST is fixed all year.
Which other cities share IRST's time zone?
IRST also covers Tehran, Isfahan, Mashhad, Tabriz, Shiraz, Karaj.
Which countries use IRST, IRST's zone?
IRST is used in Iran.
Is there a day difference between IRST and MST?
Not normally. The -10h 30m gap only pushes the date over the previous day.
What is the time difference between IRST and MST?
MST is -10h 30m from IRST.
What timezone is IRST in?
IRST operates on its local timezone.
What timezone is MST in?
MST operates on its local timezone.
Which countries use IRST (Iran Standard Time)?
IRST is used in Iran.
Does IRST observe daylight saving time?
Yes, IRST switches to IRDT during summer months.
What are some interesting facts about IRST?
IRST is one of only a few time zones with a 30-minute offset. Iran observes daylight saving time, switching to IRDT (UTC+04:30).
Which cities are in the MST timezone?
Major cities in the MST timezone include Denver, Phoenix, Salt Lake City, Calgary, Edmonton, Albuquerque, El Paso, Tucson.
What is the UTC offset for MST?
Mountain Standard Time (MST) is at UTC-07:00. During daylight saving time, it shifts to MDT.
What should I know about the MST timezone?
Arizona does not observe daylight saving time, staying on MST year-round. The Navajo Nation in Arizona does observe DST, unlike the rest of the state.
When is it midnight in IRST, what time is it in MST?
When it is 12:00 AM (midnight) in IRST (IRST), it is -10h 30m later in MST (MST).
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See every conversion from IRST →·See every conversion from MST →