I'd rather change the behaviour when saving a due date to save it on 23:59:59 instead of 00:00 rather than changing this when showing the due date.

I agree with kolaente

Ok thinking about the solution It would be like this

if form.Deadline != nil && !form.Deadline.IsZero() {
	t := form.Deadline
	deadLine := time.Date(t.Year(), t.Month(), t.Day(), 23, 59, 59, 0, t.Location())
	form.Deadline = &deadLine
	deadlineUnix = util.TimeStamp(form.Deadline.Unix())
}

This is an example for the issue deadline case. What do you think @lunny, @kolaente, @Bwko, @adelowo ? Maybe this code could be simplified.

I'd only set it to 23:59:59 if it is set to 00:00:00. Maybe someone wants to use it in some kind of frontend with exact deadlines. Or maybe don't modify it at all on the backend and only in gitea's frontend?

@rvillablanca I don't against @kolaente 's idea, but that you have to consider old data migration.

@kolaente I don't think the frontend currently supports exact deadlines.

@adelowo Ours doesn't, but the api does.

I don't think we should support exact deadlines (with time)

I have changed the behaviour of this, now the time part of a due date of issues and milestones is setted to 23:59:59 at the save/edit moment, this is according to @kolaente's suggestion.

With respect to exact deadlines I think that could be possible but at the moment due dates are being treated like a date and not like timestamp (this at least in the handlers, I know the api supports timestamp), so I believe this could be done in another PR as a new feature.