Convert GMT to JST
See the 9-hour difference from GMT to Japan Standard Time, check matching hours, and schedule calls or meetings with calendar export.
GMT to JST Conversion
Convert Greenwich Mean Time to Japan Standard Time with the exact 9-hour offset. JST is UTC+9 and does not observe daylight saving time.
Hour-by-Hour Time Table
Use the visual comparison grid and hour-by-hour table to match GMT hours to JST instantly. Pick a time slot and export it as ICS or add it to Google Calendar or Gmail.
Schedule Meetings Accurately
Find the best overlap for meetings between GMT and Japan Standard Time with automatic timezone adjustment. DST and historical timezone changes are tracked using the IANA timezone database.
How to Convert GMT to JST
Open the GMT to JST converter: Go to https://www.xconvert.com/time-converter/gmt-to-jst-converter. The page loads with GMT and JST already set up in the visual comparison grid, which is useful if you are scheduling a supplier call with Japan, lining up a London-to-Tokyo project handoff, or checking whether a UK-based support shift overlaps with business hours in Japan.
Add comparison cities if your team spans more than two locations: Click + Add City and search for cities that matter to your workflow, such as London for UK headquarters, Tokyo for Japan operations, or another GMT location used by your team in West Africa or Ireland. This is especially helpful for finance, logistics, gaming, manufacturing, and technology teams that coordinate between GMT-based offices and Japan-based partners.
Select a time range on the grid: Click Select to enter selection mode, then drag across the colored timeline on the GMT row to highlight a meeting window in purple. For example, if you drag around 9:00 GMT to 12:00 GMT, the grid shows 18:00 JST to 21:00 JST, which works for early evening coordination in Japan; if you drag to 15:00 GMT, you will see 0:00 JST the next day, confirming that late GMT afternoons push into midnight in Japan.
Export and share the result: After selecting a range, use the export options that appear: ICS download, Google Calendar, Gmail, Copy to clipboard, or Share link. This is practical when you need to send a confirmed cross-border meeting slot to a Tokyo client, add it to a distributed team calendar, or share a link with colleagues so everyone sees the same GMT-to-JST overlap without rechecking the conversion manually.
Understanding the GMT to JST Time Difference
GMT is UTC+0 and JST is UTC+9, so JST is 9 hours ahead of GMT. In practical terms, when it is 9:00 GMT, it is 18:00 JST, and when it is 12:00 GMT, it is 21:00 JST. This large eastward shift means standard daytime hours in GMT often land in the evening in Japan.
The date rollover matters as the GMT day gets later. For example, 15:00 GMT = 0:00 JST (next day) and 18:00 GMT = 3:00 JST (next day), so afternoon work in GMT can already be overnight in Japan. This is important for remote teams, customer support schedules, release planning, and travel coordination where the calendar date in Japan may already be one day ahead.
DST affects this pair because GMT is a standard-time abbreviation; its DST counterpart is IST, while JST does not observe DST. That means the GMT-to-JST difference applies when GMT is in use, but the relationship changes during the part of the year when locations such as the United Kingdom switch away from GMT to IST. Countries and territories that use GMT include the United Kingdom, Ireland, Iceland, Ghana, Senegal, Sierra Leone, Liberia, Guinea, Guinea-Bissau, Mali, Mauritania, Togo, Gambia, Burkina Faso, Ivory Coast, Sao Tome and Principe, Saint Helena, Guernsey, Jersey, and the Isle of Man, while JST is used in Japan.
Best Times for Calls and Meetings Between GMT and JST
Because JST is 9 hours ahead of GMT, the most practical overlap usually comes from morning and midday in GMT, which becomes late afternoon and evening in Japan. The clearest examples are 9:00 GMT = 18:00 JST and 12:00 GMT = 21:00 JST, giving a workable same-day window for international calls, vendor check-ins, and project updates that involve teams in GMT regions and Japan.
This makes 9:00 GMT to 12:00 GMT one of the most usable ranges for business communication. It maps to 18:00 JST to 21:00 JST, which can suit after-hours coordination in Japan for industries that regularly work across regions, including trading support, software delivery, manufacturing supply chains, shipping, and media distribution. It is often easier to ask a Japan-based team to take an early-evening call than to schedule a GMT-side meeting late enough to cross into Japan’s next morning.
Later GMT times become much harder for live meetings. 15:00 GMT = 0:00 JST (next day) and 18:00 GMT = 3:00 JST (next day), so a normal afternoon slot in GMT pushes Japanese participants into midnight or early morning. For that reason, if you are planning recurring meetings, handoffs, or client presentations, it is usually better to anchor the schedule earlier in the GMT day and use the grid to confirm whether the selected band stays inside acceptable work hours for both sides.
Frequently Asked Questions
What is the time difference between GMT and JST?
The time difference is +9 hours, with JST 9 hours ahead of GMT. That means a business day starting in a GMT location reaches Japan much later in the day, so meeting planning usually works best when the GMT side meets in the morning.
When is 9 AM GMT in JST?
9:00 GMT = 18:00 JST. This is a useful reference point for teams in the UK, Ireland, Iceland, or West Africa that need to reach colleagues or clients in Japan during the Japanese evening rather than after midnight.
When is 12 PM GMT in JST?
12:00 GMT = 21:00 JST. This can still work for urgent calls, production support, or end-of-day coordination, but it is already a late evening slot in Japan and may not suit recurring meetings.
What happens to the date when converting afternoon GMT to JST?
The date can move forward to the next day in Japan. For example, 15:00 GMT = 0:00 JST (next day) and 18:00 GMT = 3:00 JST (next day), which means a same-day afternoon meeting in GMT may already be scheduled on the following calendar day in Japan.
Does the difference between GMT and JST change during DST?
Yes, the relationship changes when places that normally use GMT move to IST, because GMT is a standard-time abbreviation; its DST counterpart is IST. JST does not observe DST, so Japan stays on the same time year-round while some GMT-based regions, including the United Kingdom, shift seasonally away from GMT.
What is the best meeting time between GMT and JST?
A practical meeting window is usually 9:00 GMT to 12:00 GMT, which corresponds to 18:00 JST to 21:00 JST. That range avoids the midnight crossover shown by 15:00 GMT = 0:00 JST (next day) and is generally better for live calls, project reviews, and customer discussions.
Which countries use GMT and which country uses JST?
GMT is used in Burkina Faso, Gambia, Ghana, Guernsey, Guinea, Guinea-Bissau, Iceland, Ireland, Isle of Man, Ivory Coast, Jersey, Liberia, Mali, Mauritania, Saint Helena, Sao Tome and Principe, Senegal, Sierra Leone, Togo, and the United Kingdom. JST is used in Japan, so this converter is especially relevant for anyone coordinating between Japan and GMT-based offices across Europe, the Atlantic islands, and West Africa.
Why is GMT to JST difficult for remote teams?
The challenge comes from the 9-hour gap, which pushes standard daytime work in GMT into evening or the next day in Japan. The examples show this clearly: 9:00 GMT = 18:00 JST is manageable, but 15:00 GMT = 0:00 JST (next day) quickly becomes impractical for routine standups, client calls, or cross-functional planning.