Conversion of times in C++ - c++

Question

This is what I am trying to do:
Get the local time (from the system);
Convert that time to the UTC format and associate it with some member variable of current object.
Later on, given the timezone of the user, I wish to convert it into the correct local time and display it to the user.
Looking up few things on SO and CppReference, I could come up with the following snippet:
#include <iostream>
#include <iomanip>
#include <ctime>
#include <string>
using namespace std;
int main()
{
time_t lt = std::time(0);
//time(0) gives current time, but LTime shows the UTC time (not local time)
string LTime = std::ctime(&lt); //localtime() gives error
cout<<LTime;
//timestamp = mktime(&tm) - timezone;
//time_t timestamp = mktime(&tm) - _timezone;
//std::cout << "timestamp: " << std::put_time(timestamp, "%c %Z") << '\n';
return 0;
}
The example on cppreference.com illustrates how the value can be printed using put_time(); but how to store it in a variable?
How to convert the UTC time format to current timezone (given some timezone as the input)? I tried using the commented code above as per this link but it does not take any parameter.

Answer 1

You can use local time get the local time and gmt time for UTC
You can set the Time zone using the list Time zone wiki
#include <iostream>
#include <iomanip>
#include <ctime>
int main()
{
std::time_t result = std::time(nullptr);
auto local = std::asctime(std::localtime(&result));
std::cout <<local;
std::cout << "UTC: " << std::put_time(std::gmtime(&result), "%c %Z") << '\n';
putenv("TZ=Asia/Singapore");
local = std::asctime(std::localtime(&result));
std::cout <<"Asia/Singapore Time "<<local;
}
Output
Thu Sep 14 21:59:37 2017
UTC: Fri Sep 15 01:59:37 2017 UTC
Asia/Singapore Time Fri Sep 15 09:59:37 2017
Program ended with exit code: 0