These instructions are out of date, but may still apply.
Note the Events pages no longer support 'News' items which do not have a 'happenning' date/time associated with them.
Always specify beginning and end dates, even when they are the same.
If you don't specify an end time, 00:00:00 will appear when you NEXT edit, and you will need to blank it out again.
If you re-edit an event with multiple days, be careful to tick that your changes should apply to all days of the event (unless you really intend otherwise).