计算 某一天据今天有多少天

- (int)intervalSinceNow: (NSString *) theDate {

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

    [date setDateFormat:@"yyyy-MM-dd"];// 传入格式 为   2017-09-18

    NSDate *d=[date dateFromString:theDate];

    

    NSTimeInterval late=[d timeIntervalSince1970]*1;

    NSDate* dat = [NSDate dateWithTimeIntervalSinceNow:0];

    NSTimeInterval now=[dat timeIntervalSince1970]*1;

    NSString *timeString=@"";

    NSTimeInterval cha=now-late;

    if (cha/86400>1) {

        timeString = [NSString stringWithFormat:@"%f", cha/86400];

        timeString = [timeString substringToIndex:timeString.length-7];

        return [timeString intValue];

    }

    return -1;

}

 

    // 1.确定时间NSString *time1 = starTime;NSString *time2 = endTime;// 2.将时间转换为dateNSDateFormatter *formatter = [[NSDateFormatter alloc] init];formatter.dateFormat = @"yyyy-MM-dd HH:mm:ss";NSDate *date1 = [formatter dateFromString:time1];NSDate *date2 = [formatter dateFromString:time2];// 3.创建日历NSCalendar *calendar = [NSCalendar currentCalendar];NSCalendarUnit type = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay | NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitSecond;// 4.利用日历对象比较两个时间的差值NSDateComponents *cmps = [calendar components:type fromDate:date1 toDate:date2 options:0];// 5.输出结果
//    NSLog(@"两个时间相差%ld年%ld月%ld日%ld小时%ld分钟%ld秒", cmps.year, cmps.month, cmps.day, cmps.hour, cmps.minute, cmps.second);NSString *timeStr = [NSString stringWithFormat:@"%ld年%ld月%ld日%ld小时%ld分钟%ld秒", cmps.year, cmps.month, cmps.day, cmps.hour, cmps.minute, cmps.second];