[tz] Some thoughts about the way forward

TJ tj at sheer.tj
Fri Sep 24 05:25:08 UTC 2021

> On Thu, Sep 23, 2021 at 6:07 PM Paul Eggert <eggert at cs.ucla.edu> wrote:
> Not really. We've done this several times before, and the compatibility issues were negligible.
As a user that will be affected by this, I am more concerned by the
practical aspects. I make extensive use of the tzdata between 1900-1970
and have data that depends on the stability of the offset calculation
from the timezone stored in the form of America/Los_Angeles, etc.

I have never used the backzone file, so I do not want to import
extensive amounts of extraneous zones, but I would like to keep the
newest changes post-1970.

How would I be able to re-build the exact tz data from 1900-1970 that is
currently available with future incremental changes? Without knowing
that, I will have to maintain my own fork forever and I'm sure others
will, too.

> If you want to maximize data stability under the constraint of being fair

> Do I really have to explain this? If we give COVID-19 shots to people in
> San Francisco but not Los Angeles, purely for reasons unrelated to
> public health, we are being unfair even though Los Angelenos' lives will
> be not be made worse - they will die off at the same rate as before.

I'm not sure I understand. Although I would prefer the tzdb to adopt
more of a linux kernel philosophy of never breaking userspace as first
principle, I don't see how this is promoting fairness either.

Perhaps I read too many of Abraham Lincoln's works when I was younger,
but I've always thought of fairness as equal opportunity rather than
absolute equality.

In that context:
1) Everyone in the world has the opportunity to add zones.
2) No one is at a systematic disadvantage to doing so.

I'm not particularly interested in a philosophical discussion about
fairness, which is much better suited to an in-person conversation,
but I just can't see how tzdb is being unfair to anyone at all. Some
volunteer added historical zones for X, Y, Z. Other volunteers can add
zones for places that they are interested in. Everyone has equal
opportunity to do so.

As far as I can see right now, this change seems more unfair to
people who have done the work to investigate and provide the data.

Is there any reason not to adopt the definition of fairness being equal
opportunity? That would maximize both stability and fairness, and also
keep the focus on improving the data.

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