Time Span
@Serializable
Represents an extent in time bounded by begin and end dateTimes.
If begin or end is missing, then that end of the period is unbounded.
The dateTime is defined according to XML Schema time (see XML Schema Part 2: Datatypes Second Edition). The value can be expressed as yyyy-mm-ddThh:mm:ss.ssszzzzzz, where T is the separator between the date and the time, and the time zone is either Z (for UTC) or zzzzzz, which represents ±hh:mm in relation to UTC. Additionally, the value can be expressed as a date only.