Checks whether the time given as a parameter is within the
interval specified by this DateInterval instance.
- p_DateTime (DateTime)
- the datetime to check
true, if p_DateTime is after the minimum time
and p_DateTime is before the maximum time.
If the minimum was not specified (has been set to null)
it returns true if p_DateTime is before the maximum time set.
If the maximum was not specified it returns true if p_DateTime is after the minimum time set.