iPhone: Notification Center Trouble
I wrote an app that allows the user to enter data in a UITextField, and one of them allows them to enter in a specific date. I'm trying to have an alert appear in the iPhones Notification Center when the date is 15 hours away. The code I wrote in my view controller is this: 

`- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    UILocalNotification *localNotif = [[UILocalNotification alloc] init];`
    
    localNotif.fireDate=[dateByAddingTimeInterval:-20*60];
    localNotif.timeZone = [NSTimeZone defaultTimeZone];
    
    
    localNotif.alertBody = @"Event tomorrow!";
    
    localNotif.alertAction = @"Show me";
    
    localNotif.soundName = UILocalNotificationDefaultSoundName;
    localNotif.applicationIconBadgeNumber = 0;
    [[UIApplication sharedApplication]presentLocalNotificationNow:localNotif];
`}`

I'm getting an error that says "Use of undeclared identifier "dateByAddingTimeInterval:"". Does anyone know how I can get past this? Thank you!
iPhone: Notification Center Trouble
===

I wrote an app that allows the user to enter data in a UITextField, and one of them allows them to enter in a specific date. I'm trying to have an alert appear in the iPhones Notification Center when the date is 15 hours away. The code I wrote in my view controller is this: 

`- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    UILocalNotification *localNotif = [[UILocalNotification alloc] init];`
    
    localNotif.fireDate=[dateByAddingTimeInterval:-20*60];
    localNotif.timeZone = [NSTimeZone defaultTimeZone];
    
    
    localNotif.alertBody = @"Event tomorrow!";
    
    localNotif.alertAction = @"Show me";
    
    localNotif.soundName = UILocalNotificationDefaultSoundName;
    localNotif.applicationIconBadgeNumber = 0;
    [[UIApplication sharedApplication]presentLocalNotificationNow:localNotif];
`}`

I'm getting an error that says "Use of undeclared identifier "dateByAddingTimeInterval:"". Does anyone know how I can get past this? Thank you!