iOS：计算两个时间的时间差

UIButton * nameButton = [UIButton buttonWithType:UIButtonTypeCustom];

nameButton.frame = CGRectMake(0, 200, self.view.frame.size.width, 100);

nameButton.backgroundColor = [UIColor orangeColor];

[self.view addSubview:nameButton];

NSCalendar *calendar = [NSCalendar currentCalendar];

NSDate *starDate = [NSDate dateWithTimeIntervalSince1970:1513142700];//开始时间

NSDate *endDate = [NSDate dateWithTimeIntervalSince1970:1513146300];//结束时间

unsigned int unitFlags = NSCalendarUnitYear| NSCalendarUnitMonth | NSCalendarUnitDay | NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitSecond ;

NSDateComponents *d = [calendar components:unitFlags fromDate:starDate toDate:endDate options:0];

[nameButton setTitle:[NSString stringWithFormat:@"%ld小时%ld分%ld秒", (long)[d hour], (long)[d minute], (long)[d second]] forState:0];