Normally DST begins at A.M. 3 or 4. If we re-use conversion operator
of local_date and local_time independently, the conversion fails if
it is the day when DST begins or ends. Since local_date considers the
time is 00:00 A.M. and local_time does not consider DST because it
does not have any date information. We need to consider both date and
time information at the same time to convert it correctly.