Unless you actually have an estimated start/end time, you should both change your properties to the following:
public DateTime WhicheverDate
{
get{ return _backingField.Date; }
set
{
if (value.Date == _backingField.date)
return;
_backingField. = value.Date;
NotifyPropertyChange("WhicheverDate");
}
}
This removes the ambiguity around the time. If you need to keep the time, obviouly this is not a solution.