System.Windows.Controls.DatePicker
It is easy to add a Datepicker control, merely add it in a BeginComposite . . . EndComposite method call. On clicking the numerical icon, it will display a month dropdown Calendar for selecting a date.
.AddAnything<DatePicker, Grid>(13, 1)
To add a background color, just set the color in a BeginSettings . . . EndSettings method call prior to adding the control to the Composite:
.Set<DatePicker, Grid>(13, 1, "Background", Brushes.WhiteSmoke)