JST to GMT Converter
Understanding JST and GMT Time Zones
Japan Standard Time (JST)
Japan Standard Time is observed in undefined and uses the offset UTC+9. Major cities in this time zone include Tokyo, Osaka, Yokohama. This time zone serves a significant global region with important economic and cultural hubs.
Greenwich Mean Time (GMT)
Greenwich Mean Time operates at UTC+0, covering undefined. Key cities include London, Dublin, Lisbon. The 9-hour backward offset from JST means that when professionals in Tokyo start their workday at 9:00 AM, it is already 12:00 AM in London.
JST is also commonly referred to as Japan time, Tokyo time, Japanese time. GMT is also known as London time, UK time, British time, England time. So if you are searching for Japan time to London time, this is the same conversion as JST to GMT.
Complete JST to GMT Conversion Table
The table below shows every two-hour increment converted from Japan Standard Time to Greenwich Mean Time. Business hours (9 AM – 5 PM) are highlighted for easy scheduling reference.
| JST (Japan Standard Time) | GMT (Greenwich Mean Time) |
|---|---|
| 12:00 AM (00:00) | 3:00 PM (15:00) (previous day) |
| 2:00 AM (02:00) | 5:00 PM (17:00) (previous day) |
| 4:00 AM (04:00) | 7:00 PM (19:00) (previous day) |
| 6:00 AM (06:00) | 9:00 PM (21:00) (previous day) |
| 8:00 AM (08:00) | 11:00 PM (23:00) (previous day) |
| 10:00 AM (10:00) | 1:00 AM (01:00) |
| 12:00 PM (12:00) | 3:00 AM (03:00) |
| 2:00 PM (14:00) | 5:00 AM (05:00) |
| 4:00 PM (16:00) | 7:00 AM (07:00) |
| 6:00 PM (18:00) | 9:00 AM (09:00) |
| 8:00 PM (20:00) | 11:00 AM (11:00) |
| 10:00 PM (22:00) | 1:00 PM (13:00) |
Times shown in 12-hour and 24-hour format. Last updated 2026-03-09.
Scheduling Between JST and GMT
When coordinating deliverables across JST and GMT, set deadlines in the earlier time zone to avoid end-of-day confusion. A "5 PM deadline" should specify which zone to prevent missed deliveries due to the 9-hour offset.
The significant 9-hour gap between JST and GMT 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 Tokyo and London
Flight times between Tokyo and London often appear misleading because of the time zone shift. A departure at 10:00 AM JST arriving at 2:00 AM GMT may look long, but remember to factor in the 9-hour offset.
Medical experts recommend allowing approximately one day of adjustment per hour of time difference. For the 9-hour shift between JST and GMT, plan for roughly one week of gradual adjustment for optimal performance.
Daylight Saving Time Considerations
Countries near the equator — including Singapore, most of Africa, and parts of South America — do not observe DST, making their offsets constant year-round. This simplifies scheduling compared to US or European zones.
For the JST to GMT conversion specifically: JST (UTC+9) does not observe DST, while GMT (UTC+0) does 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
JST (Japan Standard Time) is 9 hours ahead of GMT (Greenwich Mean Time). JST is UTC+9 and GMT is UTC+0.
When it is 12:00 PM (noon) in JST, it is 3:00 AM in GMT.
The best overlap for business hours is approximately 12:00 AM to 8:00 AM GMT, which corresponds to 9:00 AM to 5:00 PM in JST. Given the large gap, consider alternating between early and late meeting times.
Countries near the equator — including Singapore, most of Africa, and parts of South America — do not observe DST, making their offsets constant year-round. This simplifies scheduling compared to US or European zones.