C++ - Calculate the millisecond from ptime in total seconds

Question

How do i calculate the millisecond difference from the following Ptime ,I am using boost::ptime I'm trying to calculate the time_duration in milliseconds to find the difference. i get value like 999975 but expected value is 975

ptime PreviousgpsTime = Mon Jun 28 17:07:10.054 2021 ptime NextgpsTime = Mon Jun 28 17:07:11.025 2021

  double totalDiff = (NextgpsTime-PreviousgpsTime).total_milliseconds();

How to fix this and get the actual time duration.

Answer 1

Live On Coliru:

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

int main()
{
    using namespace boost::posix_time;

    ptime PreviousgpsTime = time_from_string("2021-Jun-28 17:07:10.054");
    ptime NextgpsTime     = time_from_string("2021-Jun-28 17:07:11.025");

    long totalDiff = (NextgpsTime - PreviousgpsTime).total_milliseconds();

    std::cout << "From " << PreviousgpsTime << " to " << NextgpsTime << " is " << totalDiff << "ms\n";
}

Prints

From 2021-Jun-28 17:07:10.054000 to 2021-Jun-28 17:07:11.025000 is 971ms