Ch-899 Chouchin Radio Controlled Clock Manual [best] -

Technical Report & User Manual: CH-899 Chouchin Radio Controlled Clock

6.2 12/24 Hour Format

1. Press and hold the SET button for 3 seconds.
2. Use + / – to adjust:

   While the clock is designed to update automatically, you often need to set the base time manually initially, or if the atomic signal is unavailable in your area.

   4.1 Best Practices for Reception