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

I have been working with this some time and the best regex I've came up with is the following:

\b(0)?(?(1)[1-9]|(3)?(?(2)[01]|[12][0-9]))\b|\b[1-9]\b

It will match the following numbers:

1 01 10 15 20 25 30 31

It does not match the following:

32 40 50 90