EKEventStore *eventStore = [[EKEventStore alloc] init];
    [eventStore requestAccessToEntityType:EKEntityTypeEvent completion:^(BOOL granted, NSError *error) {

// some code


}];

void (^addEventBlock)();

addEventBlock = ^
{
    NSLog(@"Hi!");
};

EKEventStore *eventStore = [[UpdateManager sharedUpdateManager] eventStore];

if ([eventStore respondsToSelector:@selector(requestAccessToEntityType:completion:)])
{
    [eventStore requestAccessToEntityType:EKEntityTypeEvent completion:^(BOOL granted, NSError *error)
     {
         if (granted)
         {
             addEventBlock();
         }
         else
         {
             NSLog(@"Not granted");
         }
     }];
}
else
{
    addEventBlock();
}

eventStore = [[EKEventStore alloc] init];

if ([eventStore respondsToSelector:@selector(requestAccessToEntityType:completion:)])
{
    [eventStore requestAccessToEntityType:EKEntityTypeEvent completion:^(BOOL granted, NSError *error)
     {
         [self performSelectorOnMainThread:@selector(addEventToCalendar) withObject:nil waitUntilDone:YES];
     }];
}
else
{
    [self addEventToCalendar];
}