The validator expects a date in yyyy-mm-dd or yyyy/mm/dd format.
You can just remove the validation from the front end (from the input) and only add it to the backend (in your server action) as the input always sends the date in yyyy-mm-dd hh:mm:ss to the server action no matter what the date format is set to. The date format option of the date picker component is only for displaying date to the users.