I have a DateTimePicker within an expander. When i open the expander the first time, the time resets to 00:00.00. From then on, the time will never reset.
<Expander>
....
<extToolkit:DateTimePicker Margin="5" MinWidth="100" Value="{Binding StartTimeDateTime}" Format="Custom" FormatString="yyyy/MM/dd,HH:mm:ss" AutoCloseCalendar="True" />
....
</Expander>