Regular Expression to match a valid day in a date

Question

I need help coming up with a regex to make sure the user enters a valid date The string will be in the format of mm/dd/yyyy

Here is what I have come up

Answer 1

Try it:
/(0?[1-9]|1[012])\/(0?[1-9]|[12][0-9]|3[01])\/((19|20)\d\d)/