CalendarDatePicker returns null when selecting the same date second time - xaml

Question

I'm using CalendarDatePicker binded to Property, and the Closed event binded to a method, both in my ViewModel. The LoadPage method uses SelectedDate property to load some data. Everything is working fine except for the time when i try to pick the same date that is picked already. In the converter i can see that the value picked is null and i get an exception because it cannot cast null to DateTimeOffset. Any idea why picked date end up being null? And how to fix this issue?
public object ConvertBack(object value, Type targetType, object parameter, string language)
{
var dateoffset = (DateTimeOffset)value;
return dateoffset.Date;
}
...
<CalendarDatePicker x:Bind ViewModel.SelectedDate,
Converter={StaticResource DateTimeConverter}, Mode=TwoWay}"
Closed="{x:Bind ViewModel.LoadPage}">
</CalendarDatePicker>

Answer 1

I have fixed it by checking in converter for null and returning DateTime.MinValue value, and then in property setter raising PropertyChanged event.
It is not really nice, i would welcome better solution.
public object ConvertBack(object value, Type targetType, object parameter, string language)
{
if (value == null) return DateTime.MinValue;
DateTimeOffset sourceTime = (DateTimeOffset)value;
DateTime targetTime = sourceTime.DateTime;
return targetTime;
}
public DateTime CurrentDate
{
get { return _currentDate; }
set
{
if (value == DateTime.MinValue)
{
RaisePropertyChanged(nameof(CurrentDate));
return;
}
Set(ref _currentDate, value);
}
}