[tz] Preparing to fork tzdb

Howard Hinnant howard.hinnant at gmail.com
Mon Sep 20 23:45:21 UTC 2021

On Sep 20, 2021, at 7:23 PM, Watson Ladd <watson at cloudflare.com> wrote:
> On Mon, Sep 20, 2021 at 9:51 AM Howard Hinnant via tz <tz at iana.org> wrote:
>> The C++20 standard has adopted the IANA timezone database (not the code) as the basis for a major part of its API:  http://eel.is/c++draft/time.zone#general-1
>> I plea for stability.  That doesn’t mean no changes.  But it does mean no drastic changes.
> Unfortunately you are held hostage to the wishes of British Canadian
> chicken farmers, Indiana counties, etc, etc. in determining what the
> zones will be.

Adding new zones is not problematic.  Removing or changing the names of existing ones is.

> The set of zones may increase due to post-1970 changes
> in ways that we cannot predict. And the C++20 standard thankfully does
> not include the list of zones in the API.

A C++20 programmer can easily obtain the list of time zone names and link names from the already standardized API:

    #include <chrono>
    #include <iostream>

        for (auto& tz : std::chrono::get_tzdb().zones)
            std::cout << tz.name() << '\n';
        for (auto& link : std::chrono::get_tzdb().links)
            std::cout << link.name() << '\n';

Current output:



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