Well, there will almost always be a technical solution for a non-technical problem.
I think the key point is not about this specific field. The whole concern here is about the disturbing trend we see these days.
Let's make some subtle yet significant changes in your statements:
1. Essentially, **today it's** just variables in userdb pointing to birth **so far**
2. It must prove the date wasn't entered randomly but by an official body **and sooner or later, it'll become mandatory**