ios时间差（与当前时间）

//写个字符串分类

- (NSString *)dateTimeDifferenceWithStartTimeEndTime

{

    NSDateFormatter *date = [[NSDateFormatteralloc]init];

    [date setDateFormat:@"yyyy-MM-dd HH:mm:ss"];

    NSDate *startD =[datedateFromString:self];

    NSDate* dat = [NSDatedate];

    

    NSTimeInterval start = [startDtimeIntervalSince1970]*1;

    NSTimeInterval end=[dattimeIntervalSince1970]*1;

    NSTimeInterval value = end - start;

    int second = (int)value %60;//秒

    int minute = (int)value /60%60;

    int house = (int)value / (3600)%24;

    int day = (int)value / (24 *3600);

    NSString *str;

    if (day !=0) {

        str = [NSStringstringWithFormat:@"%d天%d小时%d分%d秒",day,house,minute,second];

    }elseif (day==0 && house !=0) {

        str = [NSStringstringWithFormat:@"%d小时%d分%d秒",house,minute,second];

    }elseif (day== 0 && house==0 && minute!=0) {

        str = [NSStringstringWithFormat:@"%d分%d秒",minute,second];

    }else{

        str = [NSStringstringWithFormat:@"%d秒",second];

    }

    return str;

}