Dial "117" in Japan and NTT reads out the current time: "The time is 10:30 and 20 seconds. Pip, pip, pip, pong," repeating every ten seconds. The final "pong" marks the instant the announced time arrives, so that is the cue to match when you are setting the second hand on an analogue clock. The announcement follows Japan Standard Time (JST).
The service started in 1955 and has been running for more than 70 years. It was once the standard way to set a clock, and calls spiked around New Year and just before television programmes began. It is charged as an ordinary call, priced by how long you stay connected, and can be dialled from mobile phones. It is not a toll-free number, so staying on the line runs up charges.
Smartphones cut usage sharply, because they sync the clock automatically over the internet via NTP (Network Time Protocol) and never need setting by hand. Even so, as of 2026 the 117 line still earns its keep where there is no internet connection, and for adjusting analogue wall clocks that lack radio sync.
117 was still in service as of 2026 and, along with 113 (fault reporting), is one of the three-digit numbers retained as a basic telephone network service. Others have been retired: 177 (weather forecast) closed on 31 March 2025, and 104 (directory assistance) on 31 March 2026. See extinct phone numbers for the services that have gone.