You don't have a clear understanding of Cocoa memory management.
In these four lines you alloc/init a NSDate object and assign it to a local variable. On the next line you assign a different, NSDate instance to that local variable, leaking the first date. On the third line you assign the local variable to your ivar but it isn't retained. On the fourth line you release the local date variable and the ivar at the same time, even though you never retained it.
NSDate *aDate = [[NSDate alloc] init]; aDate = [datePicker date]; dateOne = aDate; [aDate release];
Try this: self.dateOne = [datePicker date];
Reread the memory management guide and the description of properties in the Obj-C 2.0 guide.