JST to MDT Converter
Understanding JST and MDT 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 Daylight Time (MDT)
Mountain Daylight Time operates at UTC-6, covering undefined. Key cities include Denver, Salt Lake City, Albuquerque. The 15-hour backward offset from JST means that when professionals in Tokyo start their workday at 9:00 AM, it is already 6:00 PM in Denver.
JST is also commonly referred to as Japan time, Tokyo time, Japanese time. MDT is also known as Mountain Time, Mountain Daylight, MT, Denver time. So if you are searching for Japan time to Mountain Time, this is the same conversion as JST to MDT.
Complete JST to MDT Conversion Table
The table below shows every two-hour increment converted from Japan Standard Time to Mountain Daylight Time. Business hours (9 AM – 5 PM) are highlighted for easy scheduling reference.
| JST (Japan Standard Time) | MDT (Mountain Daylight Time) |
|---|---|
| 12:00 AM (00:00) | 9:00 AM (09:00) (previous day) |
| 2:00 AM (02:00) | 11:00 AM (11:00) (previous day) |
| 4:00 AM (04:00) | 1:00 PM (13:00) (previous day) |
| 6:00 AM (06:00) | 3:00 PM (15:00) (previous day) |
| 8:00 AM (08:00) | 5:00 PM (17:00) (previous day) |
| 10:00 AM (10:00) | 7:00 PM (19:00) (previous day) |
| 12:00 PM (12:00) | 9:00 PM (21:00) (previous day) |
| 2:00 PM (14:00) | 11:00 PM (23:00) (previous day) |
| 4:00 PM (16:00) | 1:00 AM (01:00) |
| 6:00 PM (18:00) | 3:00 AM (03:00) |
| 8:00 PM (20:00) | 5:00 AM (05:00) |
| 10:00 PM (22:00) | 7:00 AM (07:00) |
Times shown in 12-hour and 24-hour format. Last updated 2026-03-09.
Scheduling Between JST and MDT
Remote teams spanning Tokyo and Denver often adopt asynchronous practices to bridge the 15-hour gap. Tools like Slack, Loom, and Notion reduce the need for real-time overlap while keeping projects moving forward.
The large 15-hour gap between JST and MDT 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
When arriving in Denver from Tokyo, immediately set all devices to local time. Exposure to natural daylight at the destination helps reset your circadian rhythm. Westbound travelers should seek afternoon light.
Medical experts recommend allowing approximately one day of adjustment per hour of time difference. For the 15-hour shift between JST and MDT, plan for roughly one week of gradual adjustment for optimal performance.
Daylight Saving Time Considerations
Keep in mind that DST transition dates differ between regions. The US changes clocks in March and November, Europe in March and October, and Australia in April and October. This can cause temporary shifts in conversion results.
For the JST to MDT conversion specifically: JST (UTC+9) does not observe DST, while MDT (UTC-6) does observe DST. This means the offset between them changes by one hour seasonally — the usual 15-hour gap becomes 14 or 16 hours during DST transitions.
Related Time Zone Conversions
References & Resources
Frequently Asked Questions
JST (Japan Standard Time) is 15 hours ahead of MDT (Mountain Daylight Time). JST is UTC+9 and MDT is UTC-6.
When it is 12:00 PM (noon) in JST, it is 9:00 PM (previous day) in MDT.
The best overlap for business hours is approximately 6:00 PM to 2:00 AM MDT, which corresponds to 9:00 AM to 5:00 PM in JST. Given the large gap, consider alternating between early and late meeting times.
Keep in mind that DST transition dates differ between regions. The US changes clocks in March and November, Europe in March and October, and Australia in April and October. This can cause temporary shifts in conversion results.