You will notice that when editing an event that you have 3 calendar dates to insert
Before these where manually entered as
I have installed a Date & Time picker next to each field. It is displayed as a calendar icon see screen shot.
you can now use the date time picker to save you time and headache with the date format. It uses the 24 time format still
Further if any fields currenlty display 0000-00-00 00:00:00 then you will manually adjust these and NOT CLICK the icon until saved and upated. the reason is the 00 date starts the calendar off in a negative year format of:
it is just better to manually update the field, than to use the date time picker