This object represents the beginning of the absence period.
See the documentation of the AbsencePeriod response for a full description of these fields. In particular,
note that:
- the validity of a particular time range depends on the
unit of the AbsenceType (hourly or daily)
- The times should be local times in the timezone specified by the
timezone_id field
- No timezone offset should be included (e.g no "+00:00" or "Z" suffix)