What is the time difference between MST and JST?

Japan Standard Time (JST) is 15 hours ahead of Mountain Standard Time (MST). MST uses a UTC offset of UTC-6, while JST uses UTC+9. For example, when it's 9:00 AM in MST, it's 12:00 AM in JST. 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 MST to JST?

To convert MST to JST, add 15 hours to the MST time. For example, 9:00 AM MST is 12:00 AM JST, and 5:00 PM MST is 8:00 AM JST. 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 JST when it's noon in MST?

When it's 12:00 PM (noon) in MST, it's 3:00 AM in JST. This is because JST is 15 hours ahead of MST. Similarly, when it's 6:00 PM in MST, it's 9:00 AM in JST. 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 ahead is JST from MST?

JST is 15 hours ahead of MST. This means when it's 9:00 AM in MST, it's 12:00 AM in JST, and when it's midnight in MST, it's 3:00 PM in JST. 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 JST ahead or behind MST?

JST is ahead of MST by 15 hours. Clocks in JST show a later time than MST, meaning the day starts earlier in JST relative to MST. For example, when it's morning in MST, it's already afternoon or evening in JST. This gap may change by one hour during DST transitions.

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 MST to JST conversions.

Does JST observe daylight saving time?

No, Japan Standard Time does not observe daylight saving time. The UTC offset of UTC+9 remains the same year-round, making time conversions to JST more predictable. Countries and regions in this timezone keep their clocks unchanged regardless of the season.

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

The best time for a call between MST and JST is during overlapping business hours (9 AM – 5 PM) in both timezones. To reach someone in JST during their work day, call between 6:00 PM and 2:00 AM your MST time. Avoid calling too early or late, as the 15 hours difference means your evening could be their late night. 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 MST and JST 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 MST and JST ever have the same time?

No, MST and JST never show the same time because their base UTC offsets are different. However, because MST observes daylight saving time and JST 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.

MST to JST Converter

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

Timezone Details

Mountain Standard Time

6:51 PM

Friday, April 3, 2026

MDT (UTC-06:00)

Japan Standard Time

9:51 AM

Saturday, April 4, 2026

JST (UTC+09:00)

Difference: +15 hours

MDT DST: Yes (MDT)

JST DST: No

24-Hour Overview

MDT — 24-hour overview

12a12a

3a3a

6a6a

9a9a

10a

11a

12p12p

3p3p

6p6p

9p9p

10p

11p

NightMorningBusinessEvening

JST — 24-hour overview

3p3p

6p6p

9p9p

10p

11p

12a12a

3a3a

6a6a

9a9a

10a

11a

12p12p

NightMorningBusinessEvening

Frequently Asked Questions

Related Conversions

JST to MST EST to JST JST to EST PST to JST JST to PST GMT to JST JST to GMT IST to JST JST to IST

Cities in These Timezones

MST Cities

Denver

JST Cities

Tokyo Osaka Fukuoka

More Tools

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

Learn More

How Time Zones Work Understanding DST Timezone Abbreviations

External Resources

Mountain Standard Time on Wikipedia Japan Standard Time on Wikipedia IANA Time Zone Database