Casio 4390 Manual page 56

Radio-controlled Atomic Timekeeping Precautions
• Strong electrostatic charge can result in the wrong time being set.
• The time calibration signal bounces off the ionosphere. Because of this, such factors as
changes in the reflectivity of the ionosphere, as well as movement of the ionosphere to
higher altitudes due to seasonal atmospheric changes or the time of day may change
the reception range of the signal and make reception temporarily impossible.
• Even if the time calibration signal is received properly, certain conditions can cause
the time setting to be off by up to one second.
• The current time setting in accordance with the time calibration signal takes priority
over any time settings you make manually.
• The watch is designed to update the date automatically for the period January 1,
2000 to December 31, 2099. Setting of the date by the time calibration signal will not
be performed starting from January 1, 2100.
• This watch can receive signals that differentiate between leap years and non-leap
years.
• If you are in an area where proper time calibration signal reception is impossible, the
watch keeps time with the precision noted in "Specifications".
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