This error will happen when Limit date availability is marked for an event price option, but the Start time or End time is missing.
  1. Edit the event registration form prompting this error
  2. Click Edit next to the event
  3. Under Event price options, expand the first ticket type
  4. If Limit date availability is marked, confirm a Start date and End date is entered
  5. Repeat 3-4 for any remaining Event price options
  6. Click Save
  7. Click Save
Note: Ensure you are clicking the calendar icon to set the date instead of manually typing it in.