KST ↔ GMT Time Converter

Greenwich Mean Time (GMT) is 9h behind Korea Standard Time (KST). For example, when it is 9:00 AM in KST, it is 12:00 AM in GMT. Korea Standard Time runs at UTC+9 while Greenwich Mean Time runs at UTC+0 / UTC+1 (BST). 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 KST field and the GMT result appears instantly. For a manual calculation, subtract 9h to the KST time. So noon (12:00 PM) in KST becomes 3:00 AM in GMT. 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.

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

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

Because GMT is 9h behind KST, 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 KST time — this typically keeps the GMT 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.

Korea Standard Time (KST) does not observe Daylight Saving Time and stays at a fixed UTC offset year-round. 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.

Greenwich Mean Time (GMT) also observes Daylight Saving Time, so both sides may shift at different dates, making the live converter on this page especially important. 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.

Korea Standard Time (KST) at UTC+9 covers the following major cities and regions: Seoul, Busan, Incheon, Daegu, Daejeon, Gwangju. 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.

Greenwich Mean Time (GMT) at UTC+0 / UTC+1 (BST) covers the following major cities and regions: London, Dublin, Lisbon, Reykjavik, Accra, Abidjan. 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 KST corresponds to 3:00 PM in GMT — which falls the previous 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: GMT = KST – 9h. Example: 3:00 PM KST → 6:00 AM GMT. 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.

Korea Standard Time (KST) is at UTC+9 and Greenwich Mean Time (GMT) is at UTC+0 / UTC+1 (BST). 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+9 and UTC+0 / UTC+1 (BST) gives the conversion gap of 9h behind used throughout this page.

The live converter uses your browser's built-in Intl.DateTimeFormat API backed by the IANA timezone database (IANA identifiers: Asia/Seoul for KST, Europe/London for GMT). 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.