两个时间之差
- (NSString *)intervalFromLastDate: (NSString *) dateString1  toTheDate:(NSString *) dateString2
{
    NSArray *timeArray1=[dateString1 componentsSeparatedByString:@"."];
    dateString1=[timeArray1 objectAtIndex:0];
    
    
    NSArray *timeArray2=[dateString2 componentsSeparatedByString:@"."];
    dateString2=[timeArray2 objectAtIndex:0];

    NSLog(@"%@.....%@",dateString1,dateString2);
    NSDateFormatter *date=[[NSDateFormatter alloc] init];
    [date setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
    
    
    NSDate *d1=[date dateFromString:dateString1];
    
    NSTimeInterval late1=[d1 timeIntervalSince1970]*1;
    
    
    
    NSDate *d2=[date dateFromString:dateString2];
    
    NSTimeInterval late2=[d2 timeIntervalSince1970]*1;
    
    
    
    NSTimeInterval cha=late2-late1;
    NSString *timeString=@"";
    NSString *house=@"";
    NSString *min=@"";
    NSString *sen=@"";
    
    sen = [NSString stringWithFormat:@"%d", (int)cha%60];
    //        min = [min substringToIndex:min.length-7];
//    秒
    sen=[NSString stringWithFormat:@"%@", sen];
    

   
        min = [NSString stringWithFormat:@"%d", (int)cha/60%60];
//        min = [min substringToIndex:min.length-7];
//    分
        min=[NSString stringWithFormat:@"%@", min];
        
    
//    小时
        house = [NSString stringWithFormat:@"%d", (int)cha/3600];
//        house = [house substringToIndex:house.length-7];
        house=[NSString stringWithFormat:@"%@", house];

    
    timeString=[NSString stringWithFormat:@"%@:%@:%@",house,min,sen];
        [date release];
    
    
    return timeString;
}


一个时间距现在的时间

- (NSString *)intervalSinceNow: (NSString *) theDate
{
    NSArray *timeArray=[theDate componentsSeparatedByString:@"."];
    theDate=[timeArray objectAtIndex:0];
    
    NSDateFormatter *date=[[NSDateFormatter alloc] init];
    [date setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
    NSDate *d=[date dateFromString:theDate];
    
    NSTimeInterval late=[d timeIntervalSince1970]*1;
    
    
    NSDate* dat = [NSDate date];
    NSTimeInterval now=[dat timeIntervalSince1970]*1;
    NSString *timeString=@"";
    
    NSTimeInterval cha=late-now;
    
    if (cha/3600<1) {
        timeString = [NSString stringWithFormat:@"%f", cha/60];
        timeString = [timeString substringToIndex:timeString.length-7];
        timeString=[NSString stringWithFormat:@"剩余%@分", timeString];
        
    }
    if (cha/3600>1&&cha/86400<1) {
        timeString = [NSString stringWithFormat:@"%f", cha/3600];
        timeString = [timeString substringToIndex:timeString.length-7];
        timeString=[NSString stringWithFormat:@"剩余%@小时", timeString];
    }
    if (cha/86400>1)
    {
        timeString = [NSString stringWithFormat:@"%f", cha/86400];
        timeString = [timeString substringToIndex:timeString.length-7];
        timeString=[NSString stringWithFormat:@"剩余%@天", timeString];
        
    }
    [date release];
    return timeString;
}