Asia/Tokyo

TZ identifier and aliases

Asia/Tokyo is the canonical identifier for Japan Standard Time, covering the entire country. The bare country name Japan is an older name still pointing at the same rules but is a deprecated alias — use Asia/Tokyo in new code.

UTC offset and DST rule

Asia/Tokyo is +09:00 year-round with no daylight saving time. Japan experimented with DST only once, briefly, in the early postwar years, and has kept a single fixed offset ever since — there's no seasonal clock change to account for anywhere in the country.

Using it in cron, CI and Postgres

Set TZ=Asia/Tokyo for a process that should schedule by Japanese local time. Postgres accepts it via SET TIME ZONE 'Asia/Tokyo'; or the timezone setting. Because the offset never changes, a cron job's local-time schedule behaves identically every day of the year, making Asia/Tokyo one of the operationally simplest zones in this family — there's no DST boundary, no skipped or duplicated local hour, and no need to recompute a job's UTC-equivalent trigger time across the year the way a DST-observing zone like America/New_York or Europe/Berlin requires.

History and quirks

Japan adopted a single standard time in 1888, based on the 135th meridian east passing through Akashi, well before most of Asia had standardized time zones at all. The country did try daylight saving once, imposed by the American occupying administration from 1948 to 1951 as part of postwar reconstruction policy — it proved deeply unpopular, partly because the extra evening daylight was widely seen as extending the working day rather than freeing up leisure time, and Japan dropped it the moment full sovereignty returned in 1952. Proposals to reintroduce DST have resurfaced periodically since, including ahead of the Tokyo 2020 Olympics as a way to shift outdoor events away from peak summer heat, but none has passed. At +09:00, Japan shares its exact offset with South Korea but not with China or most of Southeast Asia, despite sitting in the same general region — a reminder that East Asian time zones don't cluster as neatly as their geography might suggest.

Japan also occasionally revisits a more localized proposal — splitting Okinawa and the southern Ryukyu Islands into their own zone, closer to Taiwan's, given the archipelago's more southerly and westerly position — but like the broader DST debate, it has never gained enough political support to change Asia/Tokyo's single-zone coverage of the entire country. That stability, paired with Japan's outsized role in global electronics and automotive manufacturing, makes Asia/Tokyo one of the most heavily depended-upon zone identifiers in enterprise scheduling software worldwide, despite representing a comparatively small slice of Earth's total landmass and population relative to zones like Asia/Shanghai or America/New_York.

Offsets and DST transitions on this page are computed from the IANA time zone database bundled with your browser; the rules described above were verified against tzdata 2026b when this page was published.