TIMEWAVE / SIGNAL NOTE
JJY: Japan’s Radio Time Signals
An introduction to Japan’s JJY standard time service and the 40 kHz and 60 kHz transmissions.
JJY is Japan’s standard radio time service. Its long-wave transmissions include 40 kHz and 60 kHz services.
A radio-controlled watch must support the relevant signal and reception conditions. A model may support one service or both; check its official manual.
TimeWave modes and behavior can change by app version. Confirm the current available modes in the app before trying to sync.
Official signal references
| Carrier frequency | Transmitter | Region | Time standard | Official reference |
|---|---|---|---|---|
| 40 kHz | Ohtakadoya-yama | Fukushima, Japan | Japan Standard Time (JST) | NICT · JJY ↗ |
| 60 kHz | Hagane-yama | Saga, Japan | Japan Standard Time (JST) | NICT · JJY ↗ |
These station facts are summarized from the organizations responsible for the time services. Watch support varies by exact model; check its manual before choosing a signal.