It would be great to have a Button “Show Items without date” integrated into the Calender view so that you can drag and drop records with no date into your calender.
I think UI wise Airtable’s solution is good, however please consider adding extra filter options to such a List.
For example “Show all items without date where status ≠ done”-
In Airtable its super annoying that there is no option to hide all items that are finished already but never needed a date in the first place.