JST to KST

JST is level with KST today

On 28 August 2026, Japan Standard Time is on JST at UTC+09:00 and Korea Standard Time is on KST at UTC+09:00. The gap between them is 0 hours. So 9:00 am in JST is 9:00 am in KST, and 5:00 pm in JST is 5:00 pm in KST. Going the other way, see KST to JST.

The gap is not constant, and that is the part that catches people out

Neither zone observes daylight saving, so this is one of the few pairs where the offset really is constant all year. That is unusual: most gaps between named zones move by an hour twice a year, and by two hours during the weeks when the two ends change on different dates.

When you can actually both be at work

Taking a working day as 9:00 am to 5:00 pm local at each end, there are 8 overlapping hours in a normal day. In JST that window runs from 9:00 am to 5:00 pm, which is 9:00 am to 5:00 pm in KST. Anything outside it needs one side to start early or finish late.

Zone rules are set by legislation and change, sometimes at short notice. This page is built against tzdata 2026a, last reviewed 2026-08-18. Quarterly. Zone rules change by legislation, sometimes at short notice. Version and review date are shown on every zone page. The converter above reads your browser's own copy of the zone database, so if a rule has changed since this page was built the live answer follows the new rule — and so does everything above, which is worked out from the same database when you open the page.

Every convention used above — whether the start date counts, how month ends are clamped, which holidays close an office — is written out on the methodology page, including the daylight-saving rules behind the 0-hour gap above.