怎么计算两个日期之间相差几天及时几分

// 创建日期格式
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    dateFormatter.dateFormat = @"yyyy-MM-dd HH:mm:ss";
    // 结束时间
    NSString *endDateStr = @"2014-06-24 00:00:00";
    
    NSCalendar *calendar = [NSCalendar currentCalendar];
    unsigned int unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit;
    NSDate *nowDate = [NSDate date];
    NSDate *endDate = [dateFormatter dateFromString:endDateStr];
    
    NSDateComponents *comps = [calendar components:unitFlags fromDate:nowDate toDate:endDate options:0];
    

    NSLog(@"time-----%@",[NSString stringWithFormat:@"距离活动时间还有:%d年%d月%d天%d时%d分%d秒",comps.year,comps.month,comps.day,comps.hour,comps.minute,comps.second]);

NSDateFormatter * dateFormatter = [[NSDateFormatter alloc]init];

    [dateFormatter setDateFormat:@"yy-MM-dd HH-mm-ss"];

    NSDate * dateA = [dateFormatter dateFromString:@"2013-1-5 09-01-34"];

    NSDate * dateB = [dateFormatter dateFromString:@"2014-1-5 08-47-24"];

    NSTimeInterval timeInterval = [dateA timeIntervalSinceDate:dateB];  //这个是相隔的秒数，除以3600就是小时数，再除以24就是天数，一次类推

    NSLog(@"%f",timeInterval/3600);