Need help on date validation

We don’t know here what you’ve tried, what you are having difficulty with, and what exactly you’re trying to do (by valid, do you mean any valid date? Or is there a specific rule about what is and is not a valid date? In what timezone? etc). A single screenshot doesn’t really help anyone here understand any of that.

I assume this is part of the application you mention in your other post. If I can give you one piece of advice: just use a maintained and widely-used library for dates, dates are a nightmare to work with and you shouldn’t really be writing your own logic for anything non-trivial, it’s generally a waste of time. The date functionality in JavaScript’s standard library is very basic, use something better, i.e.