JST to MST Time Converter

Common Times Converted

JST on the left, MST on the right.

JST to MST: Full 24-Hour Conversion Table

Shaded rows are working hours; the darker shade marks the hours when both zones are at work.

What JST and MST Actually Are

JST — Japan Standard Time

Tokyo, Osaka, Yokohama, Nagoya, Sapporo. Standing at UTC+9:00 as written, and the region does not change its clocks, so that offset holds all year. Japan does not observe daylight saving, so this offset is fixed year-round.

Japan abolished daylight saving in 1952 and has resisted every attempt to reintroduce it, including a proposal around the 2020 Olympics.

MST — Mountain Standard Time

Denver, Salt Lake City, Calgary — and Phoenix year-round. Standing at UTC-7:00 as written, and the region does change its clocks, so its live offset moves by an hour twice a year. The next change is on Sunday, November 1, 2026, to MST. Arizona stays on MST all year, so Phoenix and Denver are an hour apart for eight months and identical for four.

Arizona has stayed on MST year-round since 1968 — the Navajo Nation within it does observe daylight saving, making the state a patchwork.

What This Means in Practice

The date changes mid-working-day

For 6 of the eight hours in a normal JST working day, the equivalent MST time falls on a different calendar date. Anything scheduled in that stretch needs the date checked as well as the time, or a Tuesday call quietly becomes a Wednesday one at the other end.

This gap is not fixed

MST changes its clocks and JST does not, so the difference between them moves by an hour twice a year. A recurring meeting set now will drift for one side from Sunday, November 1, 2026 unless someone resets it.

Nearly opposite sides of the clock

At 15 hours apart, one side's morning is the other side's night. Handing work over at the end of a shift usually beats trying to get both parties in the same call.

Major Cities in Each Zone

Cities on JST

Cities on MST