New Post: How to disable auto-validation in DateTimePicker.

Hi,
In v2.3, the last valid date will be set back when something invalid is set.

In the meantime, to have this behavior, you can go in file Xceed.Wpf.Toolkit/DateTimeUpDown/Implementation/DateTimeUpDown.cs, in method "TryParseDateTime", add the following lines before the return :

if( !isValid )
        result = current;