My wife lived in Granger, Indiana, in the early 1990s, and still has family both there and in Indianapolis. We were discussing the mess that is history of Indiana time zones, and she recalls a period when there was an hour difference when calling between the two cities. I was trying to find it in the history, but it would appear that Granger, being in St. Joseph Country, is considered to be in the America/Indiana/Indianapolis zone - which would preclude them ever being different.
From her recollection, she believes the entire Michiana area (https://en.wikipedia.org/wiki/Michiana) may have been in the same time zone. I've been digging but haven't found any historical reference to back that up.
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? If so, it would be quite interesting since Michiana includes the Berrien and Cass counties of Michigan, and we don't currently have those separated from America/Detroit. Of course, I'm not suggesting making a change without the appropriate evidence, but I'm wondering if anyone here has come across this in their research? Thanks, Matt