将毫秒UTC转换为人类可读日期时间 [英] Converting millisecond UTC to Human Readable Date_Time

问题描述

我很难弄清楚如何使用boost :: date_time执行转换。
我想将从Unix纪元（1970年1月1日00:00）测量的毫秒值转换为人类可读的字符串 - 例如： 2/13/2012 15:20： 11 将是理想的。

I'm struggling to figure out how to preform a conversion with boost::date_time. I want to convert a millisecond value measured from the Unix epoch (00:00, Jan 1, 1970) to a human readable string - something like: 2/13/2012 15:20:11 would be ideal.

我试过一些std C ++ /提升建议，我看到，但还没有运气。这里是我使用的代码：

I've tried some std C++ / boost suggestions I've seen but not had any luck just yet. Here is the code I use:

    long long ticksFromEpoch = 1329117220501;

    std::time_t tt = static_cast<time_t>(ticksFromEpoch);

    boost::posix_time::ptime dt = boost::posix_time::from_time_t(tt);

    // Create a time_zone_ptr for the desired time zone and use it to create a local_date_time
    boost::local_time::time_zone_ptr zone(new boost::local_time::posix_time_zone("UTC"));
    boost::local_time::local_date_time dt_with_zone(dt, zone);

    std::stringstream strm;

    strm.imbue(std::locale(std::cout.getloc(), new boost::local_time::local_time_facet("%Y-%m-%d %H:%M:%S"))); // 15:14
    strm << dt_with_zone;

    // Print the stream's content to the console
    std::cout << strm.str() << std::endl;

输出为： 2032-07-01 20:20:37 这显然不正确。我怀疑我不是正确构建 ticksFromEpoch变量，但我不知道为什么。任何人都可以指向正确的方向？任何帮助是非常感谢!!

The output is: 2032-07-01 20:20:37 which is clearly incorrect. I suspect that I'm not constructing the ticksFromEpoch variable correctly but I'm not sure why. Can anyone point me in the right direction? Any help is much appreciated!!

推荐答案

time_t 时代，而不是毫秒。
如果你不关心毫秒，你应该能够这样做：

time_t is usually seconds since "the epoch", rather than milliseconds. If you dont care about milliseconds you should be able to do this:

std::time_t tt = static_cast<time_t>(ticksFromEpoch/1000)

如果您关心毫秒，您可以将它们添加回结束（对于像12：00：00.001 AM这样的时间来说很麻烦）

If you do care about milliseconds you can either add them back in at the end (which is tricky to get right for times like 12:00:00.001 AM )

或者你需要走另一条路线。您可能需要使用这样的：（未测试）

Or you'll need to go another route. You may need to use something like this: (untested)

boost::posix_time::ptime t2(
  date(1970,Jan,1),  //The epoch
  boost::posix_time::seconds( ticksFromEpoch / 1000 ) + // Number of seconds
  boost::posix_time::microseconds( ticksFromEpoch % 1000)  // And the micros too.
  );

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