When arrow is used, there seem to be several issues/difference with how datetimes are treated compared to how this behaves without arrow. It seems the differences are most of the time when reading.

To test this, I created a PR that shows this behaviour in some added test cases: #486. Some more details can be found in a comment a bit lower in this thread.

Most likely (some of) the issues/behaviours would be best solved/changed upstream in GDAL...

@rouault