What Event markup does
It lets Google list your event with its date, place and ticket link in event results. Google requires the event name, start date and location. For in-person events the location needs an address; for online events, a link.
Mark up each event on its own page, or each event in a list. Don't mark up things that aren't events, like coupons or business hours.
When plans change
If an event is postponed, cancelled or moves online, change the status instead of deleting the markup, and keep the original date for cancelled events. Google then shows the right status to people searching.