DateTime to UTC

Question

以毫秒为单位将日期时间值转换为UTC的正确方法是什么？

我一直在寻找到std :: chrono和提升没有真正找到一个实用的方法来完成这一点，任何想法？

即

auto local_time_to_utc_milliseconds(int year, int month, int day, int hour, int minute, int second, int millisecond) -> std::uint64_t 
{ 
    return ???; 
} 

Answer 1

假设你因为 “历元”（或一些公知的时间点）的平均毫秒：

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例如

#include <boost/date_time/posix_time/posix_time.hpp> 
#include <iostream> 

int main() { 
    static const boost::posix_time::ptime epoch { { 1970, 1, 1 }, {} }; 

    auto now = boost::posix_time::microsec_clock::universal_time(); 

    std::cout << "Time in milliseconds since 1970: " << (now-epoch).total_milliseconds() << "\n"; 
} 

打印

Time in milliseconds since 1970: 1432566946471 

更新，以配合您的签名：

auto local_time_to_utc_milliseconds(boost::posix_time::ptime& dt) -> std::uint64_t 
{ 
    static const boost::posix_time::ptime epoch { { 1970, 1, 1 }, {} }; 
    return (dt - epoch).total_milliseconds(); 
} 

auto local_time_to_utc_milliseconds(int year, int month, int day, int hour, int minute, int second, int millisecond) -> std::uint64_t 
{ 
    return local_time_to_utc_milliseconds(boost::posix_time::ptime { { year, month, day }, { hour, minute, second, millisecond } }); 
}