Mod Request: Age Restrictions/Verifications

I searched for this and didn't see it suggested, although, I've found a few topics that ask for it or about it elsewhere.

I run an 18+ only site and would love to have something in place to at least try to filter the underage youngin's out. I know this isn't something all sites do, so a mod of some sort would be awesome for this.

Suggestions are open really, but I'd love to see it required for users to enter their date of birth in the profile when registering, but not have it show up on their profile except for to Admins only. If the wrong birth date is entered, then it rejects registration. I know, I know, age can be lied about, I get that, but I'd like to at least give the little one's an idea that we are at lease checking instead of them just being able to register without at least adding their birthday.

I've been able to catch a few here and there and delete their accounts, but It'd be a lot easier to cut them off at the pass. It will stop some of them from registering. I know not all though.

Like I said, I'm open for suggestions for this. I'd just like something that would help me or at least show some effort on my part.

Thanks for any helps you might give.