The XAML team has recently reviewed this issue and will not be addressing it as at this time the team is focusing on the bugs impacting the highest number of developers. If you have encountered this issue and it is blocking for your work please contact us through the support ticketing system with details on your setup and a reference to this item.
As a workaround what we could suggest you is to handle the SelectionChanged of the DateTimePicker. When DateTime gets selected for the first time you could set the SelectedTime property to the desired value and unsubscribe from the event in order the control to continue behave as expected when further items gets selected. Please, check the attached sample that demonstrates that approach.
Posted on:29 Jan 2013 09:47
I could use this all the time and it seems to me it should just be a parameter I could set in design view. PLEASE add this. It seems simple enough...