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BlogHow it works

JST to GMT Converter

Type a Tokyo time and date to see it in GMT, the UTC+0 reference. Japan has no daylight saving and GMT never moves, so the gap is the same on every date.

Japan Standard Time

JSTJapan Standard Time

GMTGreenwich Mean Time

––:––

Tokyo is 9 hours ahead of GMT on every day of the year. Subtract 9 and you have the answer.

Japan time to GMT, all 24 hours

JST timeGMT time
12:00 AM3:00 PM−1 previous day
1:00 AM4:00 PM−1 previous day
2:00 AM5:00 PM−1 previous day
3:00 AM6:00 PM−1 previous day
4:00 AM7:00 PM−1 previous day
5:00 AM8:00 PM−1 previous day
6:00 AM9:00 PM−1 previous day
7:00 AM10:00 PM−1 previous day
8:00 AM11:00 PM−1 previous day
9:00 AM12:00 AM
10:00 AM1:00 AM
11:00 AM2:00 AM
12:00 PM3:00 AM
1:00 PM4:00 AM
2:00 PM5:00 AM
3:00 PM6:00 AM
4:00 PM7:00 AM
5:00 PM8:00 AM
6:00 PM9:00 AM
7:00 PM10:00 AM
8:00 PM11:00 AM
9:00 PM12:00 PM
10:00 PM1:00 PM
11:00 PM2:00 PM
Every Tokyo hour with the GMT reading. Before 9:00 AM in Tokyo, the GMT time is on the previous day (−1).

Where the nine hours come from

Japan Standard Time is set by the 135° east meridian, the line that runs through the city of Akashi near Kobe. Because the Earth turns 15 degrees an hour, 135 degrees equals 9 hours, so JST is UTC+9 with no half hours. Japan does not use daylight saving, and the national time is generated by NICT from atomic clocks.

GMT, as used here, is the fixed UTC+0 scale, matching Coordinated Universal Time from the BIPM. With neither side moving, this page needs no list of change dates.

  • +9:00JST offset from GMT
  • 135° EJapan's reference meridian
  • 8 hTokyo ahead of London in UK summerGOV.UK

When GMT is really London time

In everyday speech GMT often stands for UK time. That only holds from the last Sunday of October to the last Sunday of March. During British Summer Time the UK is an hour ahead of GMT, so a 9:00 AM London call is 5:00 PM in Tokyo instead of 6:00 PM.

For a contact in the UK, check the live clock for London. For a fixed reference such as server logs, aviation or satellite data, keep GMT or UTC.

Common uses of a JST to GMT conversion

  • Release times for games and apps launched in Japan, often posted in JST.
  • Market hours: the Tokyo session opens at 9:00 AM JST, which is midnight GMT.
  • Reading timestamps in logs that mix UTC and Tokyo time.
  • Broadcast schedules for live events streamed from Japan.
  • Korea uses the same offset, so KST to GMT gives identical numbers.

JST to GMT questions

How many hours ahead of GMT is Japan?

Japan is 9 hours ahead of GMT all year. Subtract 9 hours from a Tokyo time to get GMT.

What is 6:00 PM JST in GMT?

6:00 PM in Tokyo is 9:00 AM GMT on the same day.

How far is Tokyo ahead of London in summer?

8 hours. London moves to BST (UTC+1) from late March to late October, while Japan stays on UTC+9.

Why is JST nine hours ahead?

Japan's standard time follows the 135° east meridian, which passes through Akashi. 135 degrees at four minutes per degree is 540 minutes, or exactly 9 hours.

Is JST the same as UTC+9?

Yes. JST is UTC+9 and GMT reads the same as UTC, so JST minus 9 hours gives both.