Why does android have a US/Michigan time zone?

Question

I noticed that android makes available a timezone for "US/Michigan". However, I can't find out what that actually is. It looks like most of Michigan is in Eastern and observes DST, and a small part of the UP is in Central and also observes DST. So why did android give them their own timezone, and why can't I find anything on the internet referencing Michigan having it's own time zone? Is this some sort of historical thing for the small number of years in the 70's that Michigan didn't observe DST?

Answer 1

This isn't related to Android specifically, but rather to the identifiers used by the IANA TZ Database, which you can read about in the timezone tag wiki, or on Wikipedia. Android is just one consumer of this data.

You can review the details of the time zones here, and you'll find that "US/Michigan" is an alias for "America/Detroit". This covers the parts of Michigan that are in the Eastern time zone.

You'll also find that Michigan has a second time zone, which is "America/Menominee", which covers the parts of Michigan that are in the Central time zone.

In general, you should use one of these two values rather than the "US/Michigan" alias. Also, if you don't care about historical time zone differences, then it would be acceptable to just use "America/Chicago" for Central time, and "America/New_York" for Eastern time.

The specific history of Michigan, including commentary, can be found in the source files of the TZ database itself. Specifically, it describes that Michigan didn't observe daylight saving time from 1968 to 1973, and that several counties switched from Eastern Time to Central Time in 1973. There are some other minor historical details as well.