appdelegate.m

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
    [self registerIntervalHotKey];
    NSManagedObjectContext *moc = [self managedObjectContext];
    Interval *interval = [NSEntityDescription insertNewObjectForEntityForName:@"Interval" inManagedObjectContext:moc];
    interval.startTime = [NSDate date];
    NSError *error = nil;
    [moc save:&error];
}

- (void)registerIntervalHotKey {
    DDHotKeyCenter *hk = [[DDHotKeyCenter alloc] init];
    DDHotKeyTask task = ^(NSEvent *hkEvent) {
        NSError *error = nil;
        NSManagedObjectContext *moc = [self managedObjectContext];
        NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Interval"];
        NSArray *results = [moc executeFetchRequest:request error:&error];
        Interval *interval = [results lastObject];
        NSLog(@"%@", interval.startTime);
    };
    if (![hk registerHotKeyWithKeyCode:21 modifierFlags:(NSControlKeyMask | NSCommandKeyMask) task:task]) {
        return;
    }
}