It appears there is no End Date or Date Repeat options for the datetime field in Drupal 8.
Are there any contrib options for recurring events in Drupal 8?
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As of 2016/03/04, these are open issues in Drupal 8. See Support for end date and D8: Date repeat feature requests. The decision was made to move these from contrib into core, but they are complicated issues, and unfortunately touch the exact same portions of code, so working on them simultaneously is difficult.
As of 2016/12/07, support for end date is officially part of core, starting with 8.2.0. It is looking like the date repeat feature is going to end up in the datetime extras module as part of contrib, and not core. However, work on this is still preliminary.
There is a new module named Date Recur Field (repeating dates) that can help you.
Recurring dates, i.e. date repeat, for Drupal 8.
Provides a new field type that supports repeating dates via recurrence rules (RRule). For RRule compilation, php-rrule is used.
I think that the module needs integration with the Datetime Range core module because for the moment to show a multi days event in Calendar you need the Improve the Views integration for DateRange fields patch.
There's a sandbox: https://www.drupal.org/sandbox/frando/2775015 - didn't test it, though.