The important part is local time plus timezone. The offset is there only for the very rare case that you save a time that you know is ambiguous when you save i

The important part is local time plus timezone. The offset is there only for the very rare case that you save a time that you know is ambiguous when you save it. And when DST rules don't change. Usually it happens when you change from DST to non-DST in the autumn and a certain hour happens twice. In the example, the offset will not be used. Only local time plus time zone. edit: I have updated the article to explain this part.