Unable to edit Date types in beta 3

[SaphuA]

What problem does this feature solve?

Currently the date values are readonly it would be awesome if these could also be edited.

What does the proposed API look like?

I guess being able to edit it as a simple string (perhaps ISO_8601 format? https://en.wikipedia.org/wiki/ISO_8601) would be enough to start with. Later on a datepicker would be even more awesome.