title: WPf Datepicker Input modification
body: <p>I am creating a form using wpf/c#. I am looking to programatically change/interpret the user's typed input in the <code>wpf toolkit DatePicker</code>. </p>
  
  <p>For example, the user types "Today", and when the control looses focus the date is interpreted and set to the current date using my c# function. </p>
  
  <p>Should I listen to the lostFocus event or is there a better way of changing how a typed input date is parsed?</p>
  
  <p>I do not care to change the display format of the date picker. I am developing this application using the mvvm pattern.</p>