JST to UTC Time Converter (Tokyo to UTC / Greenwich)
Convert JST (Japan Standard Time, Tokyo) to UTC (Coordinated Universal Time, UTC / Greenwich) instantly. View live clocks, 24-hour comparison table, best meeting overlap hours, and developer code snippets.
Interactive Hour Converter (JST → UTC)
Drag slider to test any hour24-Hour JST to UTC Time Conversion Table
Side-by-side hourly reference with business hours overlap indicators.
| JST (Tokyo) | 24h | UTC (UTC / Greenwich) | 24h | Status in UTC |
|---|---|---|---|---|
| 12:00 AM | 00:00 | 3:00 PM | 15:00 | Work Hours |
| 1:00 AM | 01:00 | 4:00 PM | 16:00 | Work Hours |
| 2:00 AM | 02:00 | 5:00 PM | 17:00 | Work Hours |
| 3:00 AM | 03:00 | 6:00 PM | 18:00 | Awake / Flex |
| 4:00 AM | 04:00 | 7:00 PM | 19:00 | Awake / Flex |
| 5:00 AM | 05:00 | 8:00 PM | 20:00 | Awake / Flex |
| 6:00 AM | 06:00 | 9:00 PM | 21:00 | Awake / Flex |
| 7:00 AM | 07:00 | 10:00 PM | 22:00 | Awake / Flex |
| 8:00 AM | 08:00 | 11:00 PM | 23:00 | Sleeping |
| 9:00 AM | 09:00 | 12:00 AM | 00:00 | Sleeping |
| 10:00 AM | 10:00 | 1:00 AM | 01:00 | Sleeping |
| 11:00 AM | 11:00 | 2:00 AM | 02:00 | Sleeping |
| 12:00 PM | 12:00 | 3:00 AM | 03:00 | Sleeping |
| 1:00 PM | 13:00 | 4:00 AM | 04:00 | Sleeping |
| 2:00 PM | 14:00 | 5:00 AM | 05:00 | Sleeping |
| 3:00 PM | 15:00 | 6:00 AM | 06:00 | Sleeping |
| 4:00 PM | 16:00 | 7:00 AM | 07:00 | Awake / Flex |
| 5:00 PM | 17:00 | 8:00 AM | 08:00 | Awake / Flex |
| 6:00 PM | 18:00 | 9:00 AM | 09:00 | Work Hours |
| 7:00 PM | 19:00 | 10:00 AM | 10:00 | Work Hours |
| 8:00 PM | 20:00 | 11:00 AM | 11:00 | Work Hours |
| 9:00 PM | 21:00 | 12:00 PM | 12:00 | Work Hours |
| 10:00 PM | 22:00 | 1:00 PM | 13:00 | Work Hours |
| 11:00 PM | 23:00 | 2:00 PM | 14:00 | Work Hours |
Developer Code Snippets (JST to UTC)
// Convert current time from JST (Asia/Tokyo) to UTC (UTC)
const now = new Date();
const inUTC = new Intl.DateTimeFormat('en-US', {
timeZone: 'UTC',
dateStyle: 'medium',
timeStyle: 'long'
}).format(now);
console.log(inUTC);# Python 3.9+ using standard zoneinfo
from datetime import datetime
from zoneinfo import ZoneInfo
dt_jst = datetime.now(ZoneInfo("Asia/Tokyo"))
dt_utc = dt_jst.astimezone(ZoneInfo("UTC"))
print(f"JST: {dt_jst.strftime('%Y-%m-%d %H:%M %Z')}")
print(f"UTC: {dt_utc.strftime('%Y-%m-%d %H:%M %Z')}")Frequently Asked Questions (JST → UTC)
How do I convert JST to UTC?
JST (Japan Standard Time) uses the IANA timezone identifier Asia/Tokyo (standard offset +09:00), while UTC (Coordinated Universal Time) uses UTC (standard offset +00:00). Use the interactive slider or the 24-hour table above to convert any hour accurately with automatic Daylight Saving Time (DST) adjustment.
What are the best meeting hours between Tokyo and UTC / Greenwich?
Check the rows highlighted with "Best Meeting Overlap" in the 24-hour table above, where both JST and UTC fall within standard 9:00 AM – 5:00 PM working hours.
Does JST to UTC account for Daylight Saving Time (DST)?
Yes. Castov uses the browser's native IANA tzdb engine (Asia/Tokyo and UTC), which automatically applies official Daylight Saving Time transitions.