Question

In Cocoa, is there a notification i can register for, that informs me, when a new day begins – at 00h:00min:01s in the morning?

Answer 1

There’s no notification that I know of. You can get a timer to fire whenever a new day begins like so:

[[NSTimer alloc] initWithFireDate:midnight
                         interval:60 * 60 * 24 //one day, in seconds
                           target:someObj
                         selector:@selector(someSelector)
                         userInfo:nil
                          repeats:YES];

The trick is getting an NSDate set to midnight. Check the Date and Time Programming Guide for how to do that with date components and the like.

EDIT: see this question for how to get the midnight NSDate.