Howard Hinnant date

howard_hinnant_date_example.cpp

/*
https://github.com/HowardHinnant/date
https://github.com/HowardHinnant/date/wiki
https://github.com/HowardHinnant/date/wiki/Examples-and-Recipes
https://github.com/HowardHinnant/date/wiki/Boost-datetime-Examples-Translated

https://howardhinnant.github.io/date/date.html
https://howardhinnant.github.io/date/tz.html
*/

string UNIX_epoch_to_local_time(size_t unix_time)
{
    auto sec = std::chrono::seconds{unix_time};

    auto time = date::sys_time<std::chrono::seconds>{sec};

    auto ita_zone = date::make_zoned("Europe/Rome", time);

    std::ostringstream oss;
    oss.imbue(std::locale("it-ch.utf8"));

    date::to_stream(oss,
                    "%A, %d %B %Y - %H:%M:%S %Z",
                    ita_zone);

    return oss.str();
}

std::tuple<string, string, string> UTC_to_excel(const std::string& input)
{
    std::istringstream ss(input);
    date::sys_seconds utc_tp; // sys_time associated with UTC timezone
    string timezone_name;

    [[maybe_unused]] const auto& stream = date::from_stream(ss, "%FT%T%Z", utc_tp, &timezone_name);
    assert(not stream.fail());
    assert(timezone_name == "Z"sv);
    
    auto current_zone_time = date::make_zoned(date::current_zone(), utc_tp);
    
    /*
    cout << "utc_time:  " << input << endl;
    cout << "rome_time: " << current_zone_time << endl;
    */
    /*{
        using namespace std::literals::chrono_literals;

        auto t_local = current_zone_time.get_local_time();
        auto today_local = std::chrono::floor<date::days>(t_local);
        date::hh_mm_ss time_local{t_local - today_local};
        date::year_month_day date_local{today_local};
        auto min = time_local.minutes().count();
        min = (min / 10) * 10;
        time_local.minutes() = std::chrono::minutes(min);

        int stoip = 0;
    }*/

    auto res = std::make_tuple(
        date::format("%d/%m/%Y", current_zone_time),
        date::format("%H:%M", current_zone_time),
        date::format("%Z", current_zone_time)
    );

    return res;
}