GMT ↔ JST Time Converter

Japan Standard Time (JST) is 9h ahead Greenwich Mean Time (GMT). For example, when it is 9:00 AM in GMT, it is 6:00 PM in JST. Greenwich Mean Time runs at UTC+0 / UTC+1 (BST) while Japan Standard Time runs at UTC+9. Always confirm with the live converter above since Daylight Saving Time can shift this offset during certain months of the year.

The quickest way is to use the live bidirectional converter at the top of this page — type any time into the GMT field and the JST result appears instantly. For a manual calculation, add 9h to the GMT time. So noon (12:00 PM) in GMT becomes 9:00 PM in JST. If the result goes past midnight, adjust by ±24 hours and note the day change. The 24-hour table further down this page also covers every hour of the day at a glance.

Japan Standard Time (JST) is 9h ahead Greenwich Mean Time (GMT). In practical terms, clocks in JST show a later time than clocks in GMT. The UTC reference points are UTC+0 / UTC+1 (BST) for GMT and UTC+9 for JST, giving a net raw difference of 9h ahead. Remember this raw figure may shift by ±1h when either zone enters or exits Daylight Saving Time.

Type a time into the JST field in the bidirectional converter above — it works equally in both directions. Manually, do the reverse: subtract 9h to the JST time to get GMT. You can also visit the dedicated JST to GMT converter page, which has its own live clocks, full table, and meeting planner for the reverse direction.

Because JST is 9h ahead GMT, the ideal scheduling window is wherever both zones overlap within 8:00 AM–6:00 PM local time. Check the meeting hours table above for exact slot recommendations. As a general rule, aim for 8:00 AM–11:00 AM GMT time — this typically keeps the JST side within a reasonable morning or afternoon window. Avoid scheduling calls that land before 7:00 AM or after 8:00 PM in either timezone, as attendance and productivity tend to suffer.

Greenwich Mean Time (GMT) observes Daylight Saving Time — its UTC offset shifts by +1 hour during summer, so the gap between GMT and JST can change by ±1h seasonally. If you are scheduling meetings or deadlines that span a DST transition, always recheck the exact offset using the live converter on this page rather than relying on a fixed-offset table, which will be off by one hour during those periods.

Japan Standard Time (JST) does not observe Daylight Saving Time, staying at a fixed offset. The live clocks and bidirectional converter on this page use the IANA timezone database and update automatically the moment DST begins or ends, so you never need to manually account for the seasonal shift.

Greenwich Mean Time (GMT) at UTC+0 / UTC+1 (BST) covers the following major cities and regions: London, Dublin, Lisbon, Reykjavik, Accra, Abidjan. Not every locality within a country necessarily follows the same standard time — some regions may use sub-zones or observe different DST rules — so always verify local time when precision matters.

Japan Standard Time (JST) at UTC+9 covers the following major cities and regions: Tokyo, Osaka, Kyoto, Yokohama, Nagoya, Sapporo, Fukuoka. As with any timezone, confirm local rules for areas near geographic or political boundaries, where the observed offset can occasionally differ from the standard definition.

Midnight (12:00 AM / 00:00) in GMT corresponds to 9:00 AM in JST — which falls the same day. This is generally outside normal business hours for both sides. Use the full 24-hour conversion table on this page to quickly look up any other reference time.

Simple formula: JST = GMT + 9h. Example: 3:00 PM GMT → 12:00 AM JST. If the result exceeds 11:59 PM, subtract 24 hours and add one day; if it goes below 12:00 AM, add 24 hours and subtract one day. This fixed formula is accurate when neither zone is in a DST transition — during transitions, rely on the live converter above.

Greenwich Mean Time (GMT) is at UTC+0 / UTC+1 (BST) and Japan Standard Time (JST) is at UTC+9. UTC (Coordinated Universal Time) is the global timekeeping standard against which all timezone offsets are defined. A positive offset like UTC+5 means the local clock is 5 hours ahead of UTC; a negative offset like UTC-5 means it is 5 hours behind. The net difference between UTC+0 / UTC+1 (BST) and UTC+9 gives the conversion gap of 9h ahead used throughout this page.

The live converter uses your browser's built-in Intl.DateTimeFormat API backed by the IANA timezone database (IANA identifiers: Europe/London for GMT, Asia/Tokyo for JST). This automatically applies DST transitions in real time, making the live clocks and converter highly accurate. The static 24-hour table uses fixed offsets and may differ by ±1 hour during DST periods — always prefer the live converter for critical scheduling.

Yes — this page is fully responsive and works on smartphones and tablets. The time input fields, swap button, and live clocks all function on iOS and Android browsers. You can also tap any row in the 24-hour conversion table to instantly load that time into the converter fields above.