here's a possible answer for setting the datepicker for 30 years before and 30 years after.
you can change the values for that..
NSCalendar *calendar = [[[NSCalendar alloc]
initWithCalendarIdentifier:NSGregorianCalendar] autorelease];
NSDate *currentDate = [NSDate date];
NSDateComponents *comps = [[[NSDateComponents alloc] init] autorelease];
[comps setYear:30];
NSDate *maxDate = [calendar dateByAddingComponents:comps toDate:currentDate options:0];
[comps setYear:-30];
NSDate *minDate = [calendar dateByAddingComponents:comps toDate:currentDate options:0];
[datePicker setMaximumDate:maxDate];
[datePicker setMinimumDate:minDate];
hope this helps..