How to get timezone abbreviation under Windows

Question

We are trying to get the timezone from std::tm with strftime:

char timezone[50];
strftime(timezone, sizeof(timezone), "%Z", &timeCreated);

On iOS, we get "EST" which is what we want. But on Windows, we get "Eastern Summer Time". Anybody know how to consistently get the current timezone in C++ in abbreviation form?

I consider making the abbreviation from the full name of the timezone by simply picking out the first character in each word. But I check the list of abbreviations and notice that we could have timezone like this one "Chuuk Time" and abbreviated as "CHUT". Which makes manually adjusting not possible.

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Not the same as Question: Windows Timezone and their abbreviations? I don't need a full list of all timezones and abbreviations. But instead, I need a systematic way to the current timezone using for example strftime. I want them to use the system's current timezone and the the current local.

Answer 1

Using this free, open-source library that has been ported to VS-2013 and later:

#include "tz.h"
#include <iostream>

int
main()
{
    using namespace std::chrono;
    using namespace date;
    std::cout << format("%Z\n", make_zoned(current_zone(), system_clock::now()));
}

This just output for me:

EDT

Fully documented.

This library uses the IANA timezone database, and when current_zone() is called, translates the current Windows timezone into the appropriate IANA timezone.