Should datepickers be inclusive or exclusive?

Does the chosen end date stop at 0:00 (exclusive) or 23:59:59 (inclusive)?

I have been changing datepickers in my company's codebase to be inclusive (assuming it was just a UX oversight by other devs), but it made me wonder whether it was just my preference more so than a convention.

Do users expect datepickers to be inclusive or exclusive, and what are the exceptions? Does the same hold true when choosing just month or year?