MST to IRST
+10h 30mMST
MSTSOURCEIRST
IRSTGreen rows indicate typical business hours (9 AM - 5 PM)
MST and IRST on the World Map
The map below highlights the MST (Mountain Standard Time) and IRST (Iran Standard Time) timezone regions across the globe.
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.
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.
Time Conversion Guide: MST to IRST
MST runs on Mountain Standard Time (MST) at UTC-07:00. IRST runs on Iran Standard Time (IRST) at UTC+03:30. That puts MST 10 hours 30 minutes ahead of IRST — a difference of +10h 30m at the current offsets.
In practice, when it is 9:00 AM in MST it is 7:30 PM in IRST. Midnight in MST is 10:30 AM in IRST. Neither zone observes daylight saving time, so the offset between them stays constant all year.
MST to IRST time conversion table
| MST (MST) | IRST (IRST) | Day |
|---|---|---|
| 12:00 AM | 10:30 AM | same day |
| 6:00 AM | 4:30 PM | same day |
| 7:00 AM | 5:30 PM | same day |
| 8:00 AM | 6:30 PM | same day |
| 9:00 AM | 7:30 PM | same day |
| 12:00 PM | 10:30 PM | same day |
| 3:00 PM | 1:30 AM | next day |
| 5:00 PM | 3:30 AM | next day |
| 6:00 PM | 4:30 AM | next day |
| 9:00 PM | 7:30 AM | next day |
Why people convert MST to IRST time
- Scheduling a call from MST to IRST: a 10:00 AM start in MST lands at 8:30 PM in IRST, so you can confirm the slot without doing the arithmetic yourself.
- Handling a +10h 30m gap: MST and IRST 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 IRST is 7:30 PM in MST.
- Coordinating a MST-based team with IRST contacts: quoting times in the other side's local clock — not your own — removes the single biggest source of missed meetings.
- Always state the zone abbreviation, not just the hour. "3:00 PM MST" 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 MST takes the early slot, the next week IRST does.
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).
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.
Best time to call between MST and IRST
With a +10h 30m offset there is no overlap inside a normal 9 AM – 5 PM day. IRST opens at 9:00 AM IRST, which is 7:30 PM in MST, so real-time calls need an early-morning or late-evening slot on one side.
Business hours overlap
MST and IRST have no shared working hours because of the +10h 30m gap. Teams need to alternate early starts or rely on asynchronous handovers.
MST is 10 hours 30 minutes ahead of IRST (MST UTC-07:00 → IRST UTC+03:30). 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
MST
☀ Currently in DST
Standard: UTC-07:00 · DST: UTC-06:00
Clocks fall back on Sun, Nov 1, 2026
IRST
Does not observe DST
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 MST and IRST?
MST (MST, UTC-07:00) is 10 hours 30 minutes ahead of IRST (IRST, UTC+03:30). The gap is currently +10h 30m.
How do I convert MST time to IRST time?
Add +10h 30m to MST local time. For example, 9:00 AM in MST is 7:30 PM in IRST.
What time is it in IRST right now?
IRST uses IRST at UTC+03:30. Use the live converter at the top of this page — it updates in real time and already accounts for the +10h 30m offset from MST.
What is the best time to call IRST from MST?
There is no shared working-hours window because of the +10h 30m gap. The closest option is 1:00 PM in MST, which is 11:30 PM in IRST.
Which is ahead, MST or IRST?
MST is 10 hours 30 minutes ahead of IRST. When it is 12:00 PM in MST it is 10:30 PM in IRST.
Does daylight saving time affect the MST–IRST difference?
Neither zone observes daylight saving time, so the +10h 30m offset between MST and IRST is fixed all year.
Which other cities share MST's time zone?
MST also covers Denver, Phoenix, Salt Lake City, Calgary, Edmonton, Albuquerque, El Paso, Tucson and 2 more.
Which countries use MST, MST's zone?
MST is used in United States (Mountain), Canada (Alberta), Mexico (Chihuahua, Sonora).
Is there a day difference between MST and IRST?
Not normally. The +10h 30m gap only pushes the date over for late-evening times.
What is the time difference between MST and IRST?
IRST is +10h 30m from MST.
What timezone is MST in?
MST operates on its local timezone.
What timezone is IRST in?
IRST operates on its local timezone.
Which countries use MST (Mountain Standard Time)?
MST is used in United States (Mountain), Canada (Alberta), Mexico (Chihuahua, Sonora).
Does MST observe daylight saving time?
Yes, MST switches to MDT during summer months.
What are some interesting facts about MST?
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.
Which cities are in the IRST timezone?
Major cities in the IRST timezone include Tehran, Isfahan, Mashhad, Tabriz, Shiraz, Karaj.
What is the UTC offset for IRST?
Iran Standard Time (IRST) is at UTC+03:30. During daylight saving time, it shifts to IRDT.
What should I know about the IRST timezone?
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).
When is it midnight in MST, what time is it in IRST?
When it is 12:00 AM (midnight) in MST (MST), it is +10h 30m later in IRST (IRST).
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See every conversion from MST →·See every conversion from IRST →