datetimepicker problem

Question

I'm pretty new to c# so i'm still trying to figure this all out. I have a datetimepicker on my form to which I only show the time. I'm trying to set the value of it when the form loads to a datetime I'm sending from another form. Anytime i try to set the value i get an exception that says "String was not recognized as a valid datetime." However if i do a catch on that exception and let it run on through it fills the time in the form correctly. I can, however, set the time to datetime.now and it works fine. Why doesn't it work when i change the value to something else? I also downloaded DateTimeExtended which allows the properties of date/time to be set and if try that and set the time to Now and then just try to change the hours/min/secs, that doesn't work either. I thought for sure that was going to work.