Field need to be required for new record created from mention date

I have created a new field in one of the module and that field needs to be required for created after any set date (i.e. 2020-10-20), that should not be required for old records. I am using the below formula to achieve this but somehow the formula is not working. Please suggest any solution.

or(not(greaterThan(strlen(toString($date_created)),0)),isAfter($date_created,date("2020-10-20")))