闰秒是否存储在 Mac OS X 的任何地方？答案

【问题标题】：Are leap seconds stored on Mac OS X anywhere?闰秒是否存储在 Mac OS X 的任何地方？
【发布时间】：2017-09-24 21:31:03
【问题描述】：

我在我的系统上运行了find /usr/share/zoneinfo/ -type f -exec file {} \; |grep -v 'no leap'，每个时区文件都说它没有闰秒。闰秒是否存储在 Mac OS X 上的任何地方，我可以以稳健的方式获取？我正在编写一个需要闰秒的库，所以我宁愿不通过网络连接，尽管进行某种系统调用是可以接受的。

【问题讨论】：

据我所知，macOS 不执行闰秒 - 相反，他们更愿意接受非常古老的时间将超过十几秒，而当您的机器跳过闰秒时，它只是表现就像网络时间服务器更正系统内部时钟错误的任何其他时间一样。基本上，Apple 的感觉是使用闰秒是浪费 CPU 周期，因为无论如何计算机时钟都不是很准确。

标签： macos time leap-second

【解决方案1】：

macOS 上的 IANA 数据库中没有存储闰秒信息：/usr/share/zoneinfo

如果您愿意使用第三方 C++11 库，Howard Hinnant's time zone library 为您提供处理闰秒的完整功能。这确实需要下载 IANA 数据库。但是您可以将此库配置为自动下载它，或者您可以手动下载它，该库将访问它。

文档有这个例子：

#include "tz.h"
#include <iostream>

int
main()
{
    using namespace date;
    using namespace std::chrono_literals;
    auto start = to_utc_time(sys_days{2015_y/jul/1} - 500ms);
    auto end = start + 2s;
    for (auto utc = start; utc < end; utc += 100ms)
    {
        auto sys = to_sys_time(utc);
        auto tai = to_tai_time(utc);
        auto gps = to_gps_time(utc);
        std::cout << format("%F %T SYS  ==  ", sys)
                  << format("%F %T %Z  ==  ", utc)
                  << format("%F %T %Z  ==  ", tai)
                  << format("%F %T %Z\n", gps);
    }
}

此示例在 2015 年 6 月插入闰秒附近迭代时间，比较系统时间、UTC、TAI 和 GPS 时钟标准：

2015-06-30 23:59:59.500 SYS  ==  2015-06-30 23:59:59.500 UTC  ==  2015-07-01 00:00:34.500 TAI  ==  2015-07-01 00:00:15.500 GPS
2015-06-30 23:59:59.600 SYS  ==  2015-06-30 23:59:59.600 UTC  ==  2015-07-01 00:00:34.600 TAI  ==  2015-07-01 00:00:15.600 GPS
2015-06-30 23:59:59.700 SYS  ==  2015-06-30 23:59:59.700 UTC  ==  2015-07-01 00:00:34.700 TAI  ==  2015-07-01 00:00:15.700 GPS
2015-06-30 23:59:59.800 SYS  ==  2015-06-30 23:59:59.800 UTC  ==  2015-07-01 00:00:34.800 TAI  ==  2015-07-01 00:00:15.800 GPS
2015-06-30 23:59:59.900 SYS  ==  2015-06-30 23:59:59.900 UTC  ==  2015-07-01 00:00:34.900 TAI  ==  2015-07-01 00:00:15.900 GPS
2015-06-30 23:59:59.999 SYS  ==  2015-06-30 23:59:60.000 UTC  ==  2015-07-01 00:00:35.000 TAI  ==  2015-07-01 00:00:16.000 GPS
2015-06-30 23:59:59.999 SYS  ==  2015-06-30 23:59:60.100 UTC  ==  2015-07-01 00:00:35.100 TAI  ==  2015-07-01 00:00:16.100 GPS
2015-06-30 23:59:59.999 SYS  ==  2015-06-30 23:59:60.200 UTC  ==  2015-07-01 00:00:35.200 TAI  ==  2015-07-01 00:00:16.200 GPS
2015-06-30 23:59:59.999 SYS  ==  2015-06-30 23:59:60.300 UTC  ==  2015-07-01 00:00:35.300 TAI  ==  2015-07-01 00:00:16.300 GPS
2015-06-30 23:59:59.999 SYS  ==  2015-06-30 23:59:60.400 UTC  ==  2015-07-01 00:00:35.400 TAI  ==  2015-07-01 00:00:16.400 GPS
2015-06-30 23:59:59.999 SYS  ==  2015-06-30 23:59:60.500 UTC  ==  2015-07-01 00:00:35.500 TAI  ==  2015-07-01 00:00:16.500 GPS
2015-06-30 23:59:59.999 SYS  ==  2015-06-30 23:59:60.600 UTC  ==  2015-07-01 00:00:35.600 TAI  ==  2015-07-01 00:00:16.600 GPS
2015-06-30 23:59:59.999 SYS  ==  2015-06-30 23:59:60.700 UTC  ==  2015-07-01 00:00:35.700 TAI  ==  2015-07-01 00:00:16.700 GPS
2015-06-30 23:59:59.999 SYS  ==  2015-06-30 23:59:60.800 UTC  ==  2015-07-01 00:00:35.800 TAI  ==  2015-07-01 00:00:16.800 GPS
2015-06-30 23:59:59.999 SYS  ==  2015-06-30 23:59:60.900 UTC  ==  2015-07-01 00:00:35.900 TAI  ==  2015-07-01 00:00:16.900 GPS
2015-07-01 00:00:00.000 SYS  ==  2015-07-01 00:00:00.000 UTC  ==  2015-07-01 00:00:36.000 TAI  ==  2015-07-01 00:00:17.000 GPS
2015-07-01 00:00:00.100 SYS  ==  2015-07-01 00:00:00.100 UTC  ==  2015-07-01 00:00:36.100 TAI  ==  2015-07-01 00:00:17.100 GPS
2015-07-01 00:00:00.200 SYS  ==  2015-07-01 00:00:00.200 UTC  ==  2015-07-01 00:00:36.200 TAI  ==  2015-07-01 00:00:17.200 GPS
2015-07-01 00:00:00.300 SYS  ==  2015-07-01 00:00:00.300 UTC  ==  2015-07-01 00:00:36.300 TAI  ==  2015-07-01 00:00:17.300 GPS
2015-07-01 00:00:00.400 SYS  ==  2015-07-01 00:00:00.400 UTC  ==  2015-07-01 00:00:36.400 TAI  ==  2015-07-01 00:00:17.400 GPS

【讨论】：