Constraint to display data with date picker

Appreciate the help from such a fantastic forum group. So great to learn from others and there are never enough short and sweet videos to clarify concepts! Hoping to lean on folks for a quick question, thank you in advance:

How would you write a constraint to display data in a text field from a certain day, using a ‘date picker’?

e.g. the ‘last modified’ data from today, if null/no data, display “enter new data”