WPF DatePicker default to today's date

please try with this ....

<my:DatePicker SelectedDate="{x:Static sys:DateTime.Now}"/>

add this reference

xmlns:sys="clr-namespace:System;assembly=mscorlib"

The below works for me. (dpDate is my DatePicker control)

public MainWindow()
{
    InitializeComponent();
    dpDate.SelectedDate = DateTime.Today;            
}