One Zone for All of Japan
Every server, phone, and calendar in Japan pulls its time from the same identifier. The National Institute of Information and Communications Technology (NICT) maintains the atomic clocks behind it. The offset is UTC+9, constant. No daylight saving time, no seasonal shifts, no exceptions.
The zone covers the entire country. Hokkaido to Okinawa, 47 prefectures, one rule. Nagoya sits at 35.181°N, 136.906°E, elevation 23 m, population 2,332,176. Its clocks match Tokyo's exactly.
| Territory | IANA Zone | Offset | DST |
|---|---|---|---|
| All of Japan (47 prefectures) | Asia/Tokyo | UTC+9 | None |
Why Nagoya Has No Zone of Its Own
The 135°E meridian, Japan's legal standard, runs through Akashi in Hyōgo Prefecture, west of both Nagoya and Tokyo. Solar noon in Nagoya arrives around 11:48 JST. In Tokyo it is closer to 11:38 JST. The clock reads the same number everywhere.
The IANA time zone collection does not mint a zone for every city. It creates zones for distinct timekeeping regions. Japan is one region. Asia/Tokyo is correct for Nagoya. Asia/Nagoya and Asia/Osaka do not exist, and searching for them returns nothing.
The Machine Name vs the Everyday Name
Asia/Tokyo is the identifier for system configuration, code, and APIs. JST (Japan Standard Time) is the abbreviation people write in emails and schedules. Both mean UTC+9, no DST, no clock changes.
How Japan's Zone Handles DST (It Doesn't)
Japan last observed daylight saving time from 1948 to 1951 under Allied occupation. Abolished in 1952. Nothing since.
What that means in practice: - No spring-forward or fall-back transitions. Ever. - When New York shifts its clocks, Japan does not move. On 15 January 2026, New York is 14 hours behind Nagoya. On 15 July 2026, New York is 13 hours behind. - London sits 9 hours behind in January, 8 in July. - Sydney is 2 hours ahead in January, 1 hour ahead in July.
Every seasonal gap change comes from the other side.
Using Japan's Zone in Code and Schedules
Set a server to Asia/Tokyo and you get a clock that never jumps. No ambiguous times during transition periods. No "fold" or "gap" edge cases.
Common scenarios:
- Server configuration: Set the TZ environment variable to Asia/Tokyo for applications serving Japanese users.
- Calendar software: Schedule recurring meetings in Asia/Tokyo so they do not drift when other zones shift.
- APIs: Pass Asia/Tokyo as the timezone parameter in datetime libraries (Python zoneinfo, JavaScript Intl.DateTimeFormat, Java ZoneId).
The absence of DST makes this one of the simplest zones to work with programmatically. No transition tables needed. UTC+9 always.
Other Japanese Cities in the IANA Collection
None. No Asia/Osaka, no Asia/Nagoya, no Asia/Fukuoka, no Asia/Sapporo. The IANA collection lists one entry for Japan.
To get local data for a Japanese city (sunrise, sunset, holidays), pair the city's coordinates with the Asia/Tokyo zone. For Nagoya, sunrise on the June solstice is 04:37, sunset 19:09. On the December solstice, sunrise is 06:56, sunset 16:43. On the March equinox, sunrise is 05:57 and sunset 18:03.