As per request, here is an example of what you need. This specific example is used to determine how long it's been since a user has created an object. It then determines whether it needs to be in minutes or hours.
NSTimeInterval timeDifference = [[NSDate date] timeIntervalSinceDate:dateToCompare;
NSTimeInterval finalTime = timeDifference / 60;
NSString *timePostedString = nil;
if (finalTime < 1) {
timePostedString = [NSString stringWithFormat:@"1m"];
} else if (finalTime >= 60) {
timePostedString = [NSString stringWithFormat:@"%.0fh", finalTime / 60];
} else if (finalTime >= 1440) {
timePostedString = [NSString stringWithFormat:@"%.1fd", finalTime / 1440];
}