The focused date for the calendar is not applied initially when setting it via code behind. If I do this via code behind: theControl.Calendar.RangeMinDate = new DateTime(2012, 1, 1); theControl.Calendar.RangeMaxDate = new DateTime(2012, 12, 31); theControl.Calendar.FocusedDate = new DateTime(2012, 1, 2); When clicking on the button to select a date, I get a "Date is out of range" message box. but then it still allows me to pick a date. The only workaround I have been able to use right now is to set the Focused date in the markup. This will allow the selection without the popup.