iOS 时间类型转换

//时间戳转时间yyyy-MM-dd
+(NSString *)getTimeFromShortTimeSp:(NSString *)shortTimeSp{
    NSTimeInterval _interval=[shortTimeSp doubleValue];
    NSDate *date = [NSDate dateWithTimeIntervalSince1970:_interval];
    NSDateFormatter *objDateformat = [[NSDateFormatter alloc] init];
    [objDateformat setDateFormat:@"yyyy-MM-dd"];
    NSString * timeStampString = [objDateformat stringFromDate: date];
    //    NSLog(@"%@", timeStampString);
    return timeStampString;
}
- (NSString *)timeFromTimestamp:(NSInteger)timestamp{

    NSLog(@"%ld", timestamp);
    NSDateFormatter *dateFormtter =[[NSDateFormatter alloc] init];
    NSDate *d = [NSDate dateWithTimeIntervalSince1970:timestamp/1000.0];
    NSTimeInterval late=[d timeIntervalSince1970]*1;    //转记录的时间戳

    NSDate* dat = [NSDate dateWithTimeIntervalSinceNow:0];
    NSTimeInterval now=[dat timeIntervalSince1970]*1;   //获取当前时间戳


    NSString *timeString=@"";
    NSTimeInterval cha=now-late;

    NSLog(@"%f", cha);
    // 发表在一小时之内
    if (cha/3600<1) {
        if (cha/60<1) {
            timeString = @"1";
        }
        else
        {
            timeString = [NSString stringWithFormat:@"%f", cha/60];
            timeString = [timeString substringToIndex:timeString.length-7];
        }

        timeString=[NSString stringWithFormat:@"%@分钟前", timeString];
    }
    // 在一小时以上24小以内
    else if (cha/3600>1&&cha/86400<1) {
        timeString = [NSString stringWithFormat:@"%f", cha/3600];
        timeString = [timeString substringToIndex:timeString.length-7];
        timeString=[NSString stringWithFormat:@"%@小时前", timeString];
    }
    // 发表在24以上10天以内
    else if (cha/86400>1&&cha/86400*3<1)     //86400 = 60(分)*60(秒)*24(小时)   3天内
    {
        timeString = [NSString stringWithFormat:@"%f", cha/86400];
        timeString = [timeString substringToIndex:timeString.length-7];
        timeString=[NSString stringWithFormat:@"%@天前", timeString];
    }
    // 发表时间大于10天
    else
    {
        [dateFormtter setDateFormat:@"yyyy-MM-dd"];
        timeString = [dateFormtter stringFromDate:d];
    }

    NSLog(@"%@", timeString);
    return timeString;
}