Casio V-REGI series Programming And Reference Manual page 98

Start and end times of scheduler are the period that scheduler
is operable. If power is not supplied or registration operation is
executed during this period, scheduler does not function until
next assigned date. To function scheduler soundly, set enough
period between start and end time. Especially, if end time is
not assigned, it determines that start time and end time are the
same giving the scheduler only one minute to function.
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