thanks for having shared the UWP controls with the community.
I'm trying to use the Calendar and I've bound its SelectedRangeDate to a DateTime SelectedDate in my viewmodel using the converter you provided and TwoWay mode.
It works ok when selecting the date from the control but I can't unselect the cell by putting in my VM SelectedDate to null (I'm using MvvmLight and its ViewModelBase for my VM, thus calling Set(ref m_SelectedDate, value) and so automagically raising the PropertyChanged event).
What I would like to achieve is having again an empty calendar, meaning with no selected cells.
What am I doing wrong?