Calendar provides adjacent dates functionality. Adjacent dates are dates belonging to the previous and next month, other than the current month. By default, the Calendar control shows adjacent dates in the calendar.

To hide the adjacent dates in the Calendar control, you can set the ShowAdjacentDay property to false.

<c1:C1Calendar x:Name="calendar" HorizontalAlignment="Left" VerticalAlignment="Top" ShowAdjacentDay="False"> </c1:C1Calendar>

This is how the Calendar looks when the adjacent dates are disabled.