It took me a few minutes to work out what the actual difference was between the 2 as well. Logically, you would think anything you put on reminders could sync with calendar. But it's not the case. Calendar is for events, things you need to go to, or big things which will happen (meetings, bdays) things like that. Whereas Reminders is for one off incidental things, such as making a phone call, lists, picking something up....