The 'Offset' parameter gives the stored UTC offset of each element in seconds, which is what tells apart the two instants a repeated wall clock names on the day a zone puts its clock back. It is accepted by the 'ConvertTo' modes listed below; those that also read it answer for the wall clock alone when it is not given.

'instant'

POSIX seconds of each element, taken from its offset by subtraction, with no time-zone lookup at all.

'fromposix'

The six components of each POSIX instant read in tzone, plus the offset in force there as a seventh output.

'rezone'

The six components of each element expressed in totzone while keeping its instant, plus the offset there as a seventh output.

'zoneoffset'

The offset the wall clock resolves to.

'keepfold'

The given offset where it still names this wall clock, and the resolved offset otherwise.

'isdst', 'zoneabbrev'

Daylight-saving flag and zone abbreviation, for the element’s own pass over a repeated clock when an offset is given.

Source Code: __datetime__