iOS - 标准时间与时间戳相互转换

做倒计时后台传的不是时间戳,是时间然后需要与系统时间对比得出时间戳进行倒计时显示

#pragma mark -- 倒计时

// 倒计时时间
        NSString* timeStr = task.receiptTime;
        NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
        [formatter setDateStyle:NSDateFormatterMediumStyle];
        [formatter setTimeStyle:NSDateFormatterShortStyle];
        [formatter setDateFormat:@"YYYY-MM-dd HH:mm:ss"]; // 设置你想要的格式,hh与HH的区别:分别表示12小时制,24小时制
        NSTimeZone* timeZone = [NSTimeZone timeZoneWithName:@"Asia/Shanghai"];
        [formatter setTimeZone:timeZone];
        NSDate* date = [formatter dateFromString:timeStr]; //倒计时时间
        NSDate *datenow = [NSDate date];//系统现在时间
        //NSString *nowtimeStr = [formatter stringFromDate:datenow];//----------将nsdate按formatter格式转成
        //时间转时间戳的方法:
        NSString *timeSp = [NSString stringWithFormat:@"%ld", (long)[date timeIntervalSince1970]];
        NSLog(@"timeSp倒计时时间戳:%@",timeSp);
        NSString *timeNow = [NSString stringWithFormat:@"%ld", (long)[datenow timeIntervalSince1970]];
        NSLog(@"timeSp系统现在时间戳:%@",timeNow);
        double timeInterval = [timeNow doubleValue]-[timeSp doubleValue];
        _countDownView.countDownTimeInterval = timeInterval;

    NSString* timeStr = @"2019-02-21 16:46:02";
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setDateStyle:NSDateFormatterMediumStyle];
    [formatter setTimeStyle:NSDateFormatterShortStyle];
    [formatter setDateFormat:@"YYYY-MM-dd HH:mm:ss"]; // ----------设置你想要的格式,hh与HH的区别:分别表示12小时制,24小时制

    //设置时区,这个对于时间的处理有时很重要
    //例如你在国内发布信息,用户在国外的另一个时区,你想让用户看到正确的发布时间就得注意时区设置,时间的换算.
    //例如你发布的时间为2010-01-26 17:40:50,那么在英国爱尔兰那边用户看到的时间应该是多少呢?
    //他们与我们有7个小时的时差,所以他们那还没到这个时间呢...那就是把未来的事做了1550738762

    NSTimeZone* timeZone = [NSTimeZone timeZoneWithName:@"Asia/Shanghai"];
    [formatter setTimeZone:timeZone];
    NSDate* date = [formatter dateFromString:timeStr]; //------------将字符串按formatter转成nsdate
    NSDate *datenow = [NSDate date];//现在时间,你可以输出来看下是什么格式
    NSString *nowtimeStr = [formatter stringFromDate:datenow];//----------将nsdate按formatter格式转成

    //时间转时间戳的方法:
    NSString *timeSp = [NSString stringWithFormat:@"%ld", (long)[date timeIntervalSince1970]];
    NSLog(@"timeSp:%@",timeSp); //时间戳的值
    //时间戳转时间的方法
    NSDate *confromTimesp = [NSDate dateWithTimeIntervalSince1970:];
    NSLog(@"1296035591  = %@",confromTimesp);
    NSString *confromTimespStr = [formatter stringFromDate:confromTimesp];
    NSLog(@"confromTimespStr =  %@",confromTimespStr);
    //时间戳转时间的方法:
    NSDateFormatter* formatter = [[NSDateFormatter alloc] init];
    [formatter setDateStyle:NSDateFormatterMediumStyle];
    [formatter setTimeStyle:NSDateFormatterShortStyle];
    [formatter setDateFormat:@"yyyyMMddHHMMss"];
    NSDate *date = [formatter dateFromString:@""];
    NSLog(@"date1:%@",date);

    //当前时间转换成秒
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    // ----------设置你想要的格式,hh与HH的区别:分别表示12小时制,24小时制
    [formatter setDateFormat:@"YYYY-MM-dd HH:mm:ss"];
    //现在时间,你可以输出来看下是什么格式
    NSDate *datenow = [NSDate date];
    //----------将nsdate按formatter格式转成nsstring
    NSString *currentTimeString = [formatter stringFromDate:datenow];
    NSLog(@"currentTimeString =  %@",currentTimeString);
    //----------将nsdate按formatter格式转成秒
    NSString *timeSp = [NSString stringWithFormat:@"%ld", (long)[datenow timeIntervalSince1970]];
    NSLog(@"timeSp = %@",timeSp);

    //时间秒转换成当前时间
    NSDate  *date = [NSDate dateWithTimeIntervalSince1970:];
    NSTimeZone *zone = [NSTimeZone systemTimeZone];
    NSInteger interval = [zone secondsFromGMTForDate: date];
    NSDate *localeDate = [date  dateByAddingTimeInterval: interval];
    NSLog(@"enddate=%@",localeDate);