There are several kind of events (default, event with no times, event with date "to be announced/determined", etc... )
so why not add a dropdown where you can select an EventType. Accordion to the option you'll see the options that should be filled. At default there will be a input for Start dateTime + End dateTime. In the default we can use a calendar-field.
ah well.. I know we shouldn't change to much in the upcoming versions but an idea pops up so am mentioning it.
// p.s. image is not JEM 2.3.0 | it's a custom/modified version of JEM2.3.0 and running within Joomla 4