Use Sugar LocalDate for calendars

[dickermoshe]

There is fairly large footgun with calendar.

The onChange callback always returns a UTC Date, however most users are working with localized dates.
The sugar package would be really helpful here (I've contributed to it in the past).

[dickermoshe]

@Pante close if you think this is unneeded/to big of a change.

[Pante]

I agree that's really gnarly to work with & I do want to eventually use Sugar's LocalDate. That said, it'll probably only happen after we have the time to clean up Sugar. There's a lot of design decisions in Sugar that I regret making.