C++14 date and time, C++ (vc++)

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#include <iostream>
#include <string>
#include <chrono>
#include <sstream>
#include <iomanip>
#include <ctime>

template < typename CLOCK_TYPE = std::chrono::system_clock >
std::string time_stamp( const typename CLOCK_TYPE::time_point& time_point, const std::string& format = "%F %T %Z (UTC%z)" )
{
    const std::time_t t = CLOCK_TYPE::to_time_t(time_point);
    const std::tm tm = *std::localtime( std::addressof(t) ) ;

std::ostringstream stm ;
    stm << std::put_time( std::addressof(tm), format.c_str() ) ;
    return stm.str() ;
}

std::string time_stamp() { return time_stamp( std::chrono::system_clock::now() ) ; }

int main()
{
     std::cout << "    now: " << time_stamp() << "\n    now: " << time_stamp( std::chrono::system_clock::now(), "%A %T") << '\n' ;

using namespace std::literals ;

// 80 hours, 18 minutes, 42 seconds earlier
     const auto earlier = std::chrono::system_clock::now() - 80h - 18min - 42s ;
     std::cout << "earlier: " << time_stamp(earlier) << '\n' ;

// 27 minutes, 30 seconds later
     const auto later = std::chrono::system_clock::now() + 27min + 30s ;
     std::cout << "  later: " << time_stamp(later) << '\n' ;
}

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Compilation time: 2,24 sec, absolute running time: 0,22 sec, absolute service time: 2,47 sec