JST to MST Converter
Understanding JST and MST Time Zones
Japan Standard Time (JST)
Japan Standard Time is observed in undefined and uses the offset UTC+9. Major cities in this time zone include Tokyo, Osaka, Yokohama. This time zone serves a significant global region with important economic and cultural hubs.
Mountain Standard Time (MST)
Mountain Standard Time operates at UTC-7, covering undefined. Key cities include Denver, Phoenix, Salt Lake City, Albuquerque. The 16-hour backward offset from JST means that when professionals in Tokyo start their workday at 9:00 AM, it is already 5:00 PM in Denver.
JST is also commonly referred to as Japan time, Tokyo time, Japanese time. MST is also known as Mountain Time, MT, Arizona time, Denver time. So if you are searching for Japan time to Mountain Time, this is the same conversion as JST to MST.
Complete JST to MST Conversion Table
The table below shows every two-hour increment converted from Japan Standard Time to Mountain Standard Time. Business hours (9 AM – 5 PM) are highlighted for easy scheduling reference.
| JST (Japan Standard Time) | MST (Mountain Standard Time) |
|---|---|
| 12:00 AM (00:00) | 8:00 AM (08:00) (previous day) |
| 2:00 AM (02:00) | 10:00 AM (10:00) (previous day) |
| 4:00 AM (04:00) | 12:00 PM (12:00) (previous day) |
| 6:00 AM (06:00) | 2:00 PM (14:00) (previous day) |
| 8:00 AM (08:00) | 4:00 PM (16:00) (previous day) |
| 10:00 AM (10:00) | 6:00 PM (18:00) (previous day) |
| 12:00 PM (12:00) | 8:00 PM (20:00) (previous day) |
| 2:00 PM (14:00) | 10:00 PM (22:00) (previous day) |
| 4:00 PM (16:00) | 12:00 AM (00:00) |
| 6:00 PM (18:00) | 2:00 AM (02:00) |
| 8:00 PM (20:00) | 4:00 AM (04:00) |
| 10:00 PM (22:00) | 6:00 AM (06:00) |
Times shown in 12-hour and 24-hour format. Last updated 2026-03-09.
Scheduling Between JST and MST
For business scheduling, the optimal overlap window between JST and MST falls roughly between 9:00 AM and 9:00 AM JST. This ensures both Tokyo and Denver teams are within standard working hours.
The large 16-hour gap between JST and MST means that finding overlapping working hours requires compromise from at least one side. Consider adopting asynchronous workflows — recorded video updates, shared documents, and time-zone-aware project management tools — to supplement the limited real-time overlap.
Travel Between Tokyo and Denver
Travelers flying from Tokyo to Denver should adjust their sleep schedule 16 days before departure at a rate of one hour per day. For this significant time difference, gradual adjustment reduces jet lag dramatically.
Medical experts recommend allowing approximately one day of adjustment per hour of time difference. For the 16-hour shift between JST and MST, plan for roughly one week of gradual adjustment for optimal performance.
Daylight Saving Time Considerations
During standard time months (November through March in the US), this offset is fixed. However, if either zone observes daylight saving time, the difference may temporarily shift by one hour during transition weeks in spring and autumn.
For the JST to MST conversion specifically: JST (UTC+9) does not observe DST, while MST (UTC-7) does observe DST. This means the offset between them changes by one hour seasonally — the usual 16-hour gap becomes 15 or 17 hours during DST transitions.
Related Time Zone Conversions
References & Resources
Frequently Asked Questions
JST (Japan Standard Time) is 16 hours ahead of MST (Mountain Standard Time). JST is UTC+9 and MST is UTC-7.
When it is 12:00 PM (noon) in JST, it is 8:00 PM (previous day) in MST.
The best overlap for business hours is approximately 5:00 PM to 1:00 AM MST, which corresponds to 9:00 AM to 5:00 PM in JST. Given the large gap, consider alternating between early and late meeting times.
During standard time months (November through March in the US), this offset is fixed. However, if either zone observes daylight saving time, the difference may temporarily shift by one hour during transition weeks in spring and autumn.