I see the date picker control in WinRT JavaScript/HTML5. Where is that control for XAML?
Note that Win 8.1 includes built-in XAML controls for DatePicker, TimePicker. So if you retarget your project to target Win 8.1 you will now get these controls.
retargeting: http://msdn.microsoft.com/en-us/library/windows/apps/dn263114.aspx