What is the time difference between IRST and MST?

Mountain Standard Time (MST) is 9 hours and 30 minutes behind Iran Standard Time (IRST). IRST uses a UTC offset of UTC+3:30, while MST uses UTC-6. For example, when it's 9:00 AM in IRST, it's 11:30 PM in MST. Note that this difference may shift by one hour during daylight saving time transitions if MST observes DST. Use the conversion table above to see the exact time for each hour of the day.

How do I convert IRST to MST?

To convert IRST to MST, subtract 9 hours and 30 minutes from the IRST time. For example, 9:00 AM IRST is 11:30 PM MST, and 5:00 PM IRST is 7:30 AM MST. Keep in mind that during daylight saving time transitions, the offset between these timezones may temporarily change by one hour. You can also use the interactive converter above for quick, accurate results.

What time is it in MST when it's noon in IRST?

When it's 12:00 PM (noon) in IRST, it's 2:30 AM in MST. This is because MST is 9 hours and 30 minutes behind IRST. Similarly, when it's 6:00 PM in IRST, it's 8:30 AM in MST. During daylight saving time transitions, these times may shift by one hour, so always verify the current offset. The color-coded conversion table above shows every hour mapped between both timezones.

How many hours behind is MST from IRST?

MST is 9 hours and 30 minutes behind IRST. This means when it's 9:00 AM in IRST, it's 11:30 PM in MST, and when it's midnight in IRST, it's 2:30 PM in MST. The exact difference can vary by one hour during daylight saving time transitions. The conversion table above provides a complete hour-by-hour mapping.

Is MST ahead or behind IRST?

MST is behind IRST by 9 hours and 30 minutes. Clocks in MST show an earlier time than IRST, meaning the day starts later in MST relative to IRST. For example, when it's noon in IRST, it's still 2:30 AM in MST. This gap may change by one hour during DST transitions.

Does IRST observe daylight saving time?

No, Iran Standard Time does not observe daylight saving time. The UTC offset of UTC+3:30 remains the same year-round, which simplifies time conversions. Regions using IRST keep their clocks unchanged regardless of the season.

Does MST observe daylight saving time?

Yes, Mountain Standard Time observes daylight saving time. During DST, the abbreviation changes to MDT and clocks move forward by one hour, typically in spring. Clocks then fall back in autumn, returning to standard MST time. This means the UTC offset for MST shifts between two values depending on the season. Check our DST change calendar for exact transition dates that may affect your IRST to MST conversions.

What is the best time to call from IRST to MST?

The best time for a call between IRST and MST is during overlapping business hours (9 AM – 5 PM) in both timezones. To reach someone in MST during their work day, call between 6:30 PM and 2:30 AM your IRST time. Avoid calling too early or late, as the 9 hours and 30 minutes difference means your evening could be their early morning. Check the color-coded conversion table above — green hours indicate business hours in both zones, making it easy to find the ideal time.

When does daylight saving time change in MST?

Daylight saving time transitions vary by year and region. Mountain Standard Time observes DST, which typically shifts clocks forward by one hour in spring ("spring forward") and back in fall ("fall back"). During these transition periods, the time difference between IRST and MST may temporarily change by one hour, which can cause confusion for scheduled meetings or calls. It's important to double-check your conversions around transition dates, especially if the two timezones switch on different dates. Check our DST change calendar for exact transition dates in the current year.

Do IRST and MST ever have the same time?

No, IRST and MST never show the same time because their base UTC offsets are different. However, because MST observes daylight saving time and IRST does not, the time difference between them changes by one hour during DST transitions. This means the gap narrows or widens depending on the season, but the two clocks never align. Always verify the current offset around DST transition dates to avoid scheduling errors.

IRST to MST Converter

Convert Iran Standard Time to Mountain Standard Time. See the hour-by-hour conversion table below.

Timezone Details

Tehran

2:11 AM

Friday, April 3, 2026

Tehran (UTC+03:30)

Mountain Standard Time

4:41 PM

Thursday, April 2, 2026

MDT (UTC-06:00)

Difference: -9h 30m

MDT DST: Yes (MDT)

24-Hour Overview

Tehran — 24-hour overview

12a12a

3a3a

6a6a

9a9a

10a

11a

12p12p

3p3p

6p6p

9p9p

10p

11p

NightMorningBusinessEvening

MDT — 24-hour overview

2p2p

5p5p

8p8p

10p

11p11p

12a

2a2a

5a5a

8a8a

10a

11a11a

12p

NightMorningBusinessEvening

Frequently Asked Questions

Related Conversions

MST to IRST MST to GMT GMT to MST

Cities in These Timezones

IRST Cities

Tehran

MST Cities

Denver

More Tools

Compare IRST & MST Plan a Meeting (IRST & MST)See on Map

Learn More

How Time Zones Work Understanding DST Timezone Abbreviations

External Resources

Mountain Standard Time on Wikipedia IANA Time Zone Database