The Events Calendar dates: _EventStartDate, _EventEndDate
Events Manager dates: _event_start, _event_end
Post type ordering
By default all post type results (posts, page, products etc..) are ordered as one group, regardless of the post type itself.
If you want to prioritize certain post type over others - for example display product results first, then posts, pages etc.. - then make sure to enable post type group ordering:
Mixed content ordering
General Options -> Ordering -> Mixed results order
If more than one result type group is active then you can order these groups here.
For example you have a search configured for Posts and BuddyPress activities. You want the BuddyPress Activities displayed first. In this case you will need to drag the "bp_activities" item above the "post_page_cpt" item:
The items in the list explained
terms - categories and terms
post_page_cpt - posts, pages and every custom post type