The time signal service announces accurate time when calling "117." Format: "The time is 10:30 and 20 seconds. Pip, pip, pip, pong" with updates every 10 seconds. Accuracy follows Japan Standard Time (JST), synchronized with NICT's cesium atomic clock.
Launched in 1955, the service has over 70 years of history. It was widely used for clock setting, especially around New Year's and before TV programs. Cost is 11 yen per call, available from mobile phones.
Smartphone adoption drastically reduced usage. Smartphones auto-sync time via NTP (Network Time Protocol), eliminating manual setting. Still, 117 remains useful in offline environments and for analog clock adjustment.
Other 3-digit services include 177 (weather), 104 (directory assistance), and 113 (fault reporting). While smartphone apps substitute most, these persist as basic telephone network services. See extinct phone numbers for discontinued services.