On 4/16/21 7:39 PM, TJ via tz wrote:
In the tz db for North America, it looks like Wisconsin is using America/Chicago which has a few rules for the time period in question: Rule Chicago 1922 1954 - Sep lastSun 2:00 0 S Rule Chicago 1955 1966 - Oct lastSun 2:00 0 S
It appears to me that Wisconsin might need some modification?
If the affected timestamps all predate 1970, we should be OK as far as tzdb is concerned, as Wisconsin would still agree with America/Chicago for timestamps after 1970. Shanks divides Wisconsin into six distinct regions depending timestamp histories before 1970. I expect that none of these histories agree with Chicago's (and I also expect that Shanks' divisions are not completely accurate, and that there may be more than six regions). Surely this would be 'backzone' file material at best, though.