JST to UTC
Tokyo to the prime meridian.
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All date & timeQuestions
What time is UTC when it is 12:00 JST?
03:00. Coordinated Universal Time is 9 hours behind Japan Standard Time, all year round. There is no hour of the standard working day that is inside 9-to-5 in both Tokyo and the prime meridian. One side has to take the call outside office hours, so it is worth agreeing which.
Is the difference between JST and UTC the same all year?
Yes. Coordinated Universal Time is 9 hours behind Japan Standard Time, all year round. Neither zone shifts in a way that changes the gap, so a time you work out once stays correct.
What do JST and UTC actually stand for?
JST is Japan Standard Time, the zone covering Tokyo, currently UTC+9 in January. UTC is Coordinated Universal Time, covering the prime meridian, at UTC+0. Fixed at UTC+9 with no daylight saving — Japan tried it briefly after the war and abandoned it. Korea runs on the same offset, so Tokyo and Seoul clocks always match.
Anything worth knowing about Coordinated Universal Time?
UTC never changes for daylight saving, which is why servers, aviation and broadcasting all run on it. It is the reference every other zone is defined against, including GMT — the two are the same clock time, but GMT is a time zone and UTC is a time standard.
When is a good time to call between Tokyo and the prime meridian?
There is no hour of the standard working day that is inside 9-to-5 in both Tokyo and the prime meridian. One side has to take the call outside office hours, so it is worth agreeing which. If the call has to happen outside that, the fairer arrangement is usually to alternate which side takes the awkward hour rather than always asking the same one.
How it works, and more about jst → utc
The difference, and whether you can rely on it
In January, Coordinated Universal Time is 9 hours behind Japan Standard Time — UTC+9 against UTC+0. It stays that way all year, so the number is worth memorising if you work across these two often.
When you can both be at a desk
There is no hour inside 9-to-5 in both Tokyo and the prime meridian. Whatever you schedule, one side is taking it outside working hours — so the useful question is not when to meet but who absorbs the inconvenience, and whether it alternates.
Reading the abbreviations literally will mislead you
JST strictly means one fixed offset, but almost nobody uses it that way. People write it to mean the time in Tokyo, which shifts if the city observes daylight saving, which this one does not. This page follows the common usage rather than the strict one, because the strict reading gives an answer that is wrong for a good part of the year.
Fixed at UTC+9 with no daylight saving — Japan tried it briefly after the war and abandoned it. Korea runs on the same offset, so Tokyo and Seoul clocks always match. UTC never changes for daylight saving, which is why servers, aviation and broadcasting all run on it. It is the reference every other zone is defined against, including GMT — the two are the same clock time, but GMT is a time zone and UTC is a time standard.
Scheduling something recurring
For a one-off, the converter above is the whole job. For a standing meeting across zones it is worth putting the invitation in a calendar that stores the zone rather than the time — then the changeover is handled for you and nobody has to remember. If you are trying to find a slot across more than two places at once, the meeting planner shows a whole day at a glance instead.