Help Restricting Date Choice in List

Siriusly one thing you could do is to restrict the columns you show in the new item window but one of them is a choice column with your 5 dates the user can select from:

Then have a simple flow in Power Automate that has the trigger of when an item is created. The first action is then to get the item then to update it. In my example the column we are updating is Birthday and I've formatted the choice column into the correct date/time format with the expression:

So, a new item is added below:

And it puts it into the calendar view.

This doesn't prevent a user from entering data into other dates, so you might want to have your initial data entry on a different then user a create item action in your flow to add it to the list with the calendar.

Rob
Los Gallardos
Microsoft Power Automate Community Super User.
Principal Consultant, SharePoint and Power Platform WSP Global (and classic 1967 Morris Traveller driver)