[tz] Michiana area (Indiana + Michigan)

[Random832]

Matt Johnson <mj1856 at hotmail.com> writes:
> I did see from the comments in the northamerica file that cover two
> counties in the Michiana area – LaPorte and Starke. LaPorte county is
> considered by tzdb to be in Western Indiana and covered by
> America/Chicago, and the Starke county has its own unique history in
> America/Indiana/Knox. Since both of those are in the Michiana area, is
> it possible that America/Indiana/Knox is actually applicable in the
> other counties of Michiana?

It's possible. It's also possible that there are some areas near the
Michigan border which observed DST in the _Eastern_ time zone,
undocumented by the tz database, which would also account for an hour
difference. Do you know if this was during the summer or winter? These
would probably be in America/New_York or America/Detroit.

It's unlikely that Starke county's _specific_ history applies to
St. Joseph county, since that history includes a USDOT petition that was
granted in 1991, whereas St. Joseph county was never (well, not since
1967) on Central time. But pre-2006 EDT usage isn't as well-documented,
since it was never strictly legal.