NSTimeInterval returns nan

[Starhopper108]

Hi, I'm simply wanting a time interval between now and a date selected by a date picker:

-(IBAction)dateChanged {
    NSTimeInterval interval = [[NSDate date] timeIntervalSinceDate:[datePicker date]];
    NSString *displayString = [NSString stringWithFormat:@"%.0f", interval];
    displayLabel.text = displayString; 
}

But the only thing it returns is nan. any help would be appreciated

[smithdale87]

My first place to look would be [datePicker date]
Do an NSLog on this value to make sure it is a valid date.