Merge pull request #323 from telerik/snenchev/d-calendar_key_exception

-Fix calendar exception thrown when switching cells

Controls/Input/Input.UWP/Calendar/View/Services/CurrencyService.cs

@@ -259,7 +259,7 @@ namespace Telerik.UI.Xaml.Controls.Input.Calendar
                 this.currentCellsToUpdate.Clear();
             }
 
-            if (oldCurrentDate != DateTime.MinValue && oldCurrentDate != newCurrentDate)
+            if (oldCurrentDate != DateTime.MinValue && oldCurrentDate.Date != newCurrentDate.Date)
             {
                 oldCurrentDate = CalendarMathHelper.GetCellDateForViewLevel(oldCurrentDate, this.Owner.DisplayMode);
                 CalendarCellModel previousCell = this.Owner.GetCellByDate(oldCurrentDate);