City history
Edo was renamed Tokyo ('Eastern Capital') in 1868 and evolved from traditional variable hours into Japan's central hub for standard time and atomic precision.
Chapter one
Earliest documented name
"Bay entrance or estuary"
Edo is the earliest documented name for the area around Tokyo Bay, appearing in late 12th-century historical chronicles such as the Azuma Kagami. Named after the Edo clan, the name literally translates to bay entrance or estuary, reflecting the original settlement situated where rivers met the bay.
Bay entrance or estuary
Originally a fortified estate of the Edo clan, Edo grew into the castle town seat of the Tokugawa shogunate in 1603 and became one of the world's most populous cities.
Eastern Capital
Renamed Tokyo on September 3, 1868, by imperial decree during the Meiji Restoration when Emperor Meiji relocated the imperial court from Kyoto to Edo Castle.
Chapter two
On January 1, 1873 (December 3, 1872 of the lunar calendar), Japan replaced its lunisolar calendar with the Gregorian solar calendar, abolishing traditional variable temporal hours.
Imperial Ordinance 51 designated the 135th meridian east (UTC+9) as the official standard time for all of Japan, taking effect nationwide on January 1, 1888.
Under the Allied GHQ occupation, Japan enacted summer time in May 1948, advancing clocks by one hour during warmer months to conserve energy.
Facing widespread resistance from workers and farmers due to long working hours and schedule disruptions, the Diet repealed summer time, reverting strictly to JST year-round.
Chapter three
Japan adopted the Western Gregorian calendar and standard 60-minute hours, bringing an end to the traditional Japanese wadokei timekeeping system.
The Tokyo Astronomical Observatory was established in Azabu (later moved to Mitaka), tasked with calculating calendars, mapping coordinates, and determining exact standard time.
Experimental reference frequency radio transmissions began in the Tokyo metropolitan area, paving the way for Japan's national time broadcast network.
High-speed bullet train service connected Tokyo and Osaka, establishing an internationally famous culture of sub-minute rail precision.