Japan Standard Time Establishment Day

What Is Japan Standard Time Establishment Day?

Every July 13th is "Japan Standard Time Establishment Day" in Japan. On July 13, 1886, the Meiji government promulgated Imperial Ordinance No. 51, establishing Japan Standard Time (日本標準時, Nihon Hyōjunji) as the time at 135 degrees East longitude — nine hours ahead of Greenwich (today's UTC+9). The new standard took effect on January 1, 1888. This decision synchronized Japan's timekeeping with international standards and unified a country that had previously operated on multiple local times, facilitating railways, telecommunications, and international commerce.

Why 135 Degrees East?

The choice of 135°E as Japan's standard meridian was both mathematically convenient and geographically logical. It passes through Akashi City in Hyogo Prefecture — close to the geographic center of the Japanese archipelago — making it a reasonable average for the country's east-west extent. More importantly, 135°E is exactly 9 × 15° east of the Prime Meridian (0°), making Japan's offset from Greenwich Mean Time a clean 9 hours. The Akashi Municipal Planetarium (明石市立天文科学館), which sits on the 135°E meridian, became Japan's symbolic "time museum."

Before Standard Time: Local Solar Times

Before standard time took effect, different regions of Japan operated on their own local solar times. This became increasingly inconvenient for railway schedules, telegraphic coordination, and international shipping. The establishment of Japan Standard Time was part of Japan's Meiji-era program of administrative and infrastructural modernization, aligning the country with the international Greenwich-based timekeeping system that was becoming the global standard in the 1880s.

Japan Standard Time Today

Japan has kept UTC+9 as its standard time. Daylight saving time was used only from 1948 to 1951, during the postwar occupation, and has been periodically debated since without being reintroduced. The country's single time zone covering an archipelago stretching over 3,000 kilometers creates some practical oddities: sunrise in eastern Hokkaido comes notably earlier than sunrise in western Okinawa on the same calendar date. Japan's atomic clocks at the National Institute of Information and Communications Technology (NICT) maintain the official time standard with extraordinary precision.

Fun Facts

• Daylight saving, briefly: Japan used daylight saving time only from 1948 to 1951. Proposals to bring it back have come up several times, but none has been adopted.
• Two time zones, once: From 1896 to 1937, a "Western Standard Time" based on 120°E was used in the Yaeyama and Miyako Islands and in Taiwan, then under Japanese rule.
• A Meiji-era ordinance still in force: The 1886 imperial ordinance that set Japan Standard Time remains in effect today as a cabinet order.
• Akashi: The city of Akashi in Hyogo Prefecture celebrates its identity as the "city of time" (時のまち), with meridian markers and the Akashi Municipal Planetarium.