Re: [Boost-users] convert separate year, month, day, hour, minute, secs, ms to milliseconds since epoch

Subject: Re: [Boost-users] convert separate year, month, day, hour, minute, secs, ms to milliseconds since epoch
From: Sergey Spiridonov (sena_at_[hidden])
Date: 2019-03-11 14:50:47

On Sun, 3 Mar 2019 12:45:17 -0800
Victor Yankee via Boost-users <boost-users_at_[hidden]> wrote:

> I am using C++14 and boost 1.64.0 (could move to newest boost), and
> need to convert date and time pieces to a single value for
> milliseconds since the epoch. This is what I have:
> 
> int64_t msSinceEpoch(int year,int month,int day,int hour,int
> minute,int second,int ms)
>             {
>             struct std::tm t;
>             t.tm_sec    = second;
>             t.tm_min    = minute;
>             t.tm_hour   = hour;
>             t.tm_mday   = day;
>             t.tm_mon    = month-1;
>             t.tm_year   = year-1900;
>             t.tm_isdst  = 0;
>             return (1000* timegm(&t))+ms; // is timegm cross-platform?
>             }
> 
> Is there a better way?

Sorry, previous was for seconds

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

int64_t time_msec_since_epoch(int year, int month, int day,
                    int hour, int minute, int second, int msec) 
{ 
  static const boost::posix_time::ptime
        epoch(boost::gregorian::date(1970,1,1));

  boost::posix_time::ptime pt(
      boost::gregorian::date(year, month, day),
      boost::posix_time::time_duration(hour, minute, second) +
      boost::posix_time::milliseconds(msec)
  );

  boost::posix_time::time_duration since_epoch = pt - epoch;
  return since_epoch.total_milliseconds(); 
}

-- 
Best regards, Sergey Spiridonov