NSDates contain both date and time. From the docs:
NSDate objects represent a single point in time.
In the example below, the current date and time are indicated as the minimum value and the time per hour from this value as the maximum value (to check it, just put it in the viewDidLoad of any UIViewController):
NSDate *minDate = [NSDate new];
NSDate *maxDate = [[NSDate alloc] initWithTimeIntervalSinceNow:60*60];
UIDatePicker *picker = [UIDatePicker new];
[picker setDatePickerMode:UIDatePickerModeDateAndTime];
[picker setMinimumDate:minDate];
[picker setMaximumDate:maxDate];
[[self view] addSubview:picker];
[super viewDidLoad];
NSDate Dev Center.