Nice idea! It isn't possible at the moment (although you could sort of do it with a validated text input or even a series of questions using selects for day/month/year).

I also like the idea of having a date input! Using a text input with a completion designed similar to path completion is in my opinion a user-friendly implementation of that feature. Parsing the input to a date could then easily be done via the dateparser project for example.

It's already done :) I will send you a PR this afternoon