JST vs KST time zone comparison

How JST and KST compare

Japan Standard Time (JST) sits at UTC+09:00 today, while Korea Standard Time (KST) is at UTC+09:00. The current gap is 0 hours, with JST ahead of KST. In practical terms, if your morning starts at 9 AM in Tokyo, your counterpart in Seoul is seeing 09:00 on their own watch at that exact moment.

JST is the working clock for Tokyo, Osaka and Yokohama. KST covers Seoul, Busan and Incheon. If your team is split between these two regions, the table above is the quickest way to spot the daily overlap window without doing the offset arithmetic in your head.

Neither JST nor KST observes daylight saving in the modern era, which is unusual and convenient: the gap between the two zones stays the same in January and in July. You can quote the offset once and forget about it.

Common scheduling traps are easy to avoid here. Pick a wall-clock time on one side, read the matching wall-clock on the other from the table, and write both into the calendar invite, never just the difference. If the meeting falls in the week of a DST changeover and one of these zones shifts, the absolute clock will drift by an hour from what the recipient expects. The table is computed for today's date, so for a future meeting open the converter linked above and pick the exact date.

One last note for asynchronous teams: business-hour overlap is the wrong metric for handoff workflows. If you operate on a follow-the-sun model, you actually want zero overlap, with one team logging off as the other starts. JST and KST share a clock, so this model does not apply between them. Pick distant zones instead.