Jean, Per theory.html <https://data.iana.org/time-zones/theory.html>, "[a]lthough a named location in the tz database stands for the containing region, its pre-1970 data entries are often accurate for only a small subset of that region." In particular, pre-1970 data in America/Chicago is only intended to be correct for Chicago, IL, so timestamps for the example locations you gave (Duluth, MN; Conway, AR; Port Arthur, TX) may of course differ according to local custom at the time. Pre-1970 data is not considered in the scope of the tz project: "Although 1970 is a somewhat-arbitrary cutoff, there are significant challenges to moving the cutoff earlier even by a decade or two, due to the wide variety of local practices before computer timekeeping became prevalent." -- Tim Parenti On Wed, 13 Nov 2019 at 03:17, Jean <jc@jcremers.com> wrote:
I forgot to mention, another famous person Joplin, Janis 19/01/1943 09:45:00 Port Arthur TX, United States, 93w57, 29n53, America/Chicago
Olson database gives the same as astrodatabank, 5 hours. This is to show that the results are not consequently wrong. My impression is that the area is so big there are expceptions but i'm a layman so..
On 12/11/2019 21:23, Paul Eggert wrote:
On 11/9/19 3:51 AM, Jean via tz wrote:
There are other problems, like the America/Chicago timezone which is notorious for giving false results for years before 1970
Although Matt addressed your other points, I'm curious about this one. In what sense is tzdb's America/Chicago "notorious" for being wrong? I used Google to search for '"America/Chicago" false results' and the only hits I came up with were downstream bugs (e.g., in PHP installation, or in mistaken use of Python primitives), not bugs in tzdb itself.