[tz] Issues with pre-1970 information in TZDB

Howard Hinnant howard.hinnant at gmail.com
Wed Sep 22 22:23:21 UTC 2021

On Sep 22, 2021, at 5:17 PM, Tom Lane via tz <tz at iana.org> wrote:
> One thing that's particularly sticking in my craw about the
> changes under debate is that they undeniably made tzdb worse as a
> description of reality in the places at issue.

This is my objection as well.  Before the change the tzdb does a “best effort” on pre-1970 dates.  After the change it’s as if we are intentionally putting in data known to be incorrect and different from the correct data we had.

People who consume this data have no clue that there is a 1970 border, and no way to change whatever tzdb version their vendor provides for them.

And in an ideal world, when said consumer runs her program on a different platform, she would get the same results.  We shouldn’t make that portability less likely.  We should not create multiple competing versions of the database, whether hosted separately or together.  The latest released version should have the most accurate data to the best of our ability.  Otherwise we get https://xkcd.com/927/ .

Giving vendors competing versions of this database hurts everyone involved:

* It hurts the vendors because they have to spend time figuring out what they ship.
* It hurts library and application programmer because it makes their code less portable.
* It hurts people using programs because they can get different answers when switching products or platforms.
* It hurts the reputation of this project in the eyes of those who discover that we purposefully made such a mess.

Maybe it was a mistake to put pre-1970 data into the tzdb.  But that decision was made long ago, and this genie can not be stuffed back into the bottle.  Now we have to deal with the fact that people are using pre-1970 data.


More information about the tz mailing list