[C++20] Examples of the new time zone features in <chrono>

main.cpp

#include <chrono>
#include <iostream>

// Requires clang 17 or gcc 13

int main()
{
    // UTC (system_clock is guaranteed to be UTC since C++20)
    const auto now = std::chrono::system_clock::now();
    std::cout << "UTC time = " << now << '\n';

    // Local
    const auto local_now = std::chrono::zoned_time{std::chrono::current_zone(), now};
    std::cout << "Local time = " << local_now << "\n";

    // Somewhere
    const auto somewhere_tz = std::chrono::locate_zone("Asia/Ho_Chi_Minh");
    const auto somewhere_now = std::chrono::zoned_time{somewhere_tz, now};
    std::cout << somewhere_tz->name() << " time = " << somewhere_now << '\n';

    // Possible time zone names
    const auto &tzdb = std::chrono::get_tzdb();
    std::cout << "Database version = " << tzdb.version << '\n';
    for (auto &tz : tzdb.zones)
    {
        std::cout << "  - " << tz.name() << "\n";
    }
}