When searching for the locale-specific flexible day period for a given
hour, we were neglecting to handle cases where the period crosses 00:00.
For example, the en locale defines a day period range of [21:00, 06:00).
When given the hour of 05:00, we were checking if (21 <= 5 && 5 < 6),
thus not recognizing that the hour falls in that period.
