#include <iostream>
#include <ctime> // ******* C++ header for std::gmtime() etc.

int main()
{
    std::time_t now = std::time(nullptr) ;

    // make a copy of the std::tm
    std::tm modified_time = *std::gmtime( &now ) ;

    // modify the copy as you please
    modified_time.tm_sec = 0 ; // set seconds to zero
    modified_time.tm_year += 6 ; // move to six years later
    // etc...

    std::cout << "UTC: " << std::asctime( &modified_time ) ;
}