(Photo by Luis Samayoa / Stripes Okinawa)
The clock does not always stop at midnight in Japan.
Those up late at night might notice a curious 30-hour timekeeping system used in Japan.
Rather than resetting the day at 00:00, midnight, the 30-hour clock continues counting through the early morning hours. A show listed at 25:00 airs at 1 a.m. A train leaving at 27:00 departs at 3 a.m. This system of timekeeping stretches as far as 30:00, or 6 a.m., before the next business day begins.
This unusual timekeeping format started in Japanese astronomy pre-WWII for researchers keeping logs overnight. By extending the day beyond 24 hours, astronomers avoided confusion caused by switching dates in the middle of their shift.
The practice soon spread beyond astronomy, however.
After World War II, Japan’s railways adopted the system in printed timetables published by Kotsu Shimbunsha. These overnight train departure times were listed as 24:00 and beyond, keeping schedules tied to the day the journey began. A Thursday night departure at 25:30 was understood as Thursday’s last train, not Friday morning’s first train.
In the 1960s, this practice moved to broadcast. Radio stations began filling the wee hours with music and talk. In 1967, Nippon Broadcasting System, Inc. launched “All Night Nippon,” a late-night radio show that proudly ran from 25:00 to 27:00.
When television expanded into the late-night slots, it followed suit. TV guides nationwide printed programs using the 30-hour clock, cementing the clock as part of Japanese pop culture.
In Okinawa, the 30-hour clock is used throughout the prefecture, particularly among broadcast stations and businesses open into the early morning hours.
The Ryukyu Broadcasting Corporation (RBC) uses the extended clock format for its programming day with a 28-hour clock for both radio and television broadcasting. The RBC starts its programming day at 4 a.m. and ends the day at 28:00 or 3 a.m.
In the United States, the clock does not extend beyond 24 hours, but the concept of early morning hour programming belonging to the previous day is similar.
For instance, “Saturday Night Live” airs live at roughly 11:30 p.m. Eastern Time. The program is 90 minutes with a majority of the program airing on Sunday morning, yet the show is associated with Saturday because the early hours of Sunday morning are still widely viewed as Saturday night by the American public.
The Naha International Airport lists its parking lot hours as open from 06:00 to 24:00, noting plane delays can cause the lot’s operating hours to extend beyond 24:00. Rollup Burrito in Koza is open until 25:00 on Friday (Saturday at 1 a.m.) and 26:00 on Saturday (Sunday at 2 a.m.).
In these cases, the time goes beyond the traditional 24-hour clock to avoid ambiguity caused by the traditional 24-hour clock.
Since the Naha International Airport closes at night, any delay that causes workers to stay later than midnight and the parking lot to remain open is part of the previous business day, not the ensuing day.
Likewise, this applies to customers. A customer grabbing a meal at 1 a.m. after a day out would consider their meal the last meal of the previous day, not a current-day breakfast.
Although many Japanese associate early morning hours with the previous day, this usage does not extend to ordinary conversation.
When asked how Okinawans would say that they were going to a restaurant at 25:00, Okinawa native Daisuke Tsuchiya said, “we will say 1 [a.m.].”
In Japan, time does not stop at midnight, it just keeps going.
Austin Howton is a U.S. Air Force Contracting Officer and licensed attorney that has been stationed at Kadena since November of 2023. He enjoys reading, travelling, and exploring the intersections of law, government and global affairs.
AloJapan.com