What is MST in JST?
Japan Standard Time is 15 hours ahead
Mountain Time is on UTC−6:00 and Japan Standard Time is on UTC+9:00 right now. Mountain Time is on daylight saving, so its clocks read MDT. The gap changes during the year — see below.
- Time in Denver
- 8:56 pm
- Time in Tokyo
- 11:56 am
- Difference
- +15 h
- Next clock change
- November 1, 2026
Convert a time
JST — Japan Standard Time
11:00 am
Wed, the next day
When the difference changes
Mountain Time and Japan Standard Time do not change their clocks on the same dates, so the gap between them is not the same all year. Most converters show only today’s figure. These are the periods ahead:
- Now – November 1, 2026Japan Standard Time is 15 hours ahead
- November 1, 2026 – March 14, 2027Japan Standard Time is 16 hours ahead
- March 14, 2027 – onwardsJapan Standard Time is 15 hours ahead
Periods shorter than a day are not listed: both zones change at 2am in their own local time, so there are a few hours on each transition date when the gap is briefly something else.
Daylight saving
Mountain Time
Clocks go back one hour at 2am local time, becoming MST.
Japan Standard Time
Japan Standard Time stays on JST all year, so its offset from UTC never moves.
MST to JST conversion table
Every hour of Tuesday, September 22, 2026, converted from Mountain Time to Japan Standard Time. 15 of the 24 hours fall on a different calendar day in Tokyo, which is marked.
- 12:00 am MDT
- 3:00 pm JST
- 1:00 am MDT
- 4:00 pm JST
- 2:00 am MDT
- 5:00 pm JST
- 3:00 am MDT
- 6:00 pm JST
- 4:00 am MDT
- 7:00 pm JST
- 5:00 am MDT
- 8:00 pm JST
- 6:00 am MDT
- 9:00 pm JST
- 7:00 am MDT
- 10:00 pm JST
- 8:00 am MDT
- 11:00 pm JST
- 9:00 am MDT
- 12:00 am JST+1 day
- 10:00 am MDT
- 1:00 am JST+1 day
- 11:00 am MDT
- 2:00 am JST+1 day
- 12:00 pm MDT
- 3:00 am JST+1 day
- 1:00 pm MDT
- 4:00 am JST+1 day
- 2:00 pm MDT
- 5:00 am JST+1 day
- 3:00 pm MDT
- 6:00 am JST+1 day
- 4:00 pm MDT
- 7:00 am JST+1 day
- 5:00 pm MDT
- 8:00 am JST+1 day
- 6:00 pm MDT
- 9:00 am JST+1 day
- 7:00 pm MDT
- 10:00 am JST+1 day
- 8:00 pm MDT
- 11:00 am JST+1 day
- 9:00 pm MDT
- 12:00 pm JST+1 day
- 10:00 pm MDT
- 1:00 pm JST+1 day
- 11:00 pm MDT
- 2:00 pm JST+1 day
Scheduling between the two
There is no overlap between a nine-to-six working day in Denver and one in Tokyo — the gap is too wide. A call has to sit early or late for one side. Early morning in Denver is the usual compromise, since that is late afternoon or evening in Tokyo.
Mountain Time (MDT) is used in Salt Lake City, Albuquerque and Calgary. Arizona keeps MST all year and does not follow MDT.