GMT to JST Converter
Understanding GMT and JST Time Zones
Greenwich Mean Time (GMT)
Greenwich Mean Time is observed in undefined and uses the offset UTC+0. Major cities in this time zone include London, Dublin, Lisbon. This time zone covers parts of Europe and/or Africa, home to major financial and cultural centers.
Japan Standard Time (JST)
Japan Standard Time operates at UTC+9, covering undefined. Key cities include Tokyo, Osaka, Yokohama. The 9-hour forward offset from GMT means that when professionals in London start their workday at 9:00 AM, it is already 6:00 PM in Tokyo.
GMT is also commonly referred to as London time, UK time, British time, England time. JST is also known as Japan time, Tokyo time, Japanese time. So if you are searching for London time to Japan time, this is the same conversion as GMT to JST.
Complete GMT to JST Conversion Table
The table below shows every two-hour increment converted from Greenwich Mean Time to Japan Standard Time. Business hours (9 AM – 5 PM) are highlighted for easy scheduling reference.
| GMT (Greenwich Mean Time) | JST (Japan Standard Time) |
|---|---|
| 12:00 AM (00:00) | 9:00 AM (09:00) |
| 2:00 AM (02:00) | 11:00 AM (11:00) |
| 4:00 AM (04:00) | 1:00 PM (13:00) |
| 6:00 AM (06:00) | 3:00 PM (15:00) |
| 8:00 AM (08:00) | 5:00 PM (17:00) |
| 10:00 AM (10:00) | 7:00 PM (19:00) |
| 12:00 PM (12:00) | 9:00 PM (21:00) |
| 2:00 PM (14:00) | 11:00 PM (23:00) |
| 4:00 PM (16:00) | 1:00 AM (01:00) (next day) |
| 6:00 PM (18:00) | 3:00 AM (03:00) (next day) |
| 8:00 PM (20:00) | 5:00 AM (05:00) (next day) |
| 10:00 PM (22:00) | 7:00 AM (07:00) (next day) |
Times shown in 12-hour and 24-hour format. Last updated 2026-03-09.
Scheduling Between GMT and JST
Freelancers and contractors working across GMT and JST should clearly state their invoicing time zone. A 9-hour difference means an "end of business day" deliverable could mean very different things to each party.
The significant 9-hour gap between GMT and JST means that finding overlapping working hours requires compromise from at least one side. Consider adopting asynchronous workflows — recorded video updates, shared documents, and time-zone-aware project management tools — to supplement the limited real-time overlap.
Travel Between London and Tokyo
For layover planning between undefined and undefined destinations, connecting flights often involve intermediate time zones. Use our converter to verify each leg independently to avoid missed connections.
Medical experts recommend allowing approximately one day of adjustment per hour of time difference. For the 9-hour shift between GMT and JST, plan for roughly one week of gradual adjustment for optimal performance.
Daylight Saving Time Considerations
Some regions within a time zone do not observe DST. Arizona (MST) and Hawaii (HST) stay on standard time year-round, which can create unexpected offsets with neighboring states during summer months.
For the GMT to JST conversion specifically: GMT (UTC+0) observes DST, while JST (UTC+9) does not observe DST. This means the offset between them changes by one hour seasonally — the usual 9-hour gap becomes 8 or 10 hours during DST transitions.
Related Time Zone Conversions
References & Resources
Frequently Asked Questions
GMT (Greenwich Mean Time) is 9 hours behind JST (Japan Standard Time). GMT is UTC+0 and JST is UTC+9.
When it is 12:00 PM (noon) in GMT, it is 9:00 PM in JST.
The best overlap for business hours is approximately 6:00 PM to 2:00 AM JST, which corresponds to 9:00 AM to 5:00 PM in GMT. Given the large gap, consider alternating between early and late meeting times.
Some regions within a time zone do not observe DST. Arizona (MST) and Hawaii (HST) stay on standard time year-round, which can create unexpected offsets with neighboring states during summer months.