Mountain Standard Time is 15 hours behind Japan Standard Time.

Frequently asked

Quick answers about converting between Mountain Standard Time and Japan Standard Time. Can't find what you need? Email [email protected].

What is the time difference between Mountain Standard Time and Japan Standard Time?

Mountain Standard Time is 15 hours behind Japan Standard Time right now. We always show the live, daylight-saving-correct difference, so this figure already accounts for whichever side is observing summer time today.

When it's 9am in Mountain Standard Time, what time is it in Japan Standard Time?

9am in Mountain Standard Time is 12am in Japan Standard Time on the next day. Use the hour-by-hour table above to read any other time across — find the row and read the matching cell in the other column.

What's the best time for a call between Mountain Standard Time and Japan Standard Time?

There's no comfortable 9-to-5 overlap between Mountain Standard Time and Japan Standard Time — they sit on opposite sides of the planet's working day. Plan for an early or late call on one side, or hand work off asynchronously.

Does this account for daylight saving time?

Yes. We track every clock change in both places, so the abbreviations you see — MDT and JST — are the ones actually in effect right now, not a fixed all-year value. When either side changes its clocks, this page updates automatically.

Why is the date sometimes different on each side?

When two places are far enough apart, the same moment can fall on different calendar days. That is why some conversions are marked "previous day" or "next day" — it is the same instant in time, read off two clocks that crossed midnight at different points.