Casio 4390 Manual page 29

Note
• When a calibration time is reached, the watch will receive the calibration signal only
if it is in either the Timekeeping Mode or World Time Mode. Reception is not
performed if a calibration time is reached while you are configuring settings.
• Auto receipt of the calibration signal is designed to be performed early in the
morning, while you sleep (provided that the Timekeeping Mode time is set correctly).
Before going to bed for the night, remove the watch from your wrist, and put it in a
location where it can receive the signal easily.
• Remember that reception of the calibration signal depends on the current time in the
Timekeeping Mode.
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