> The real issue is that when setting the tzname tuple in the time module, we use a guess based on the value of tm_zone probed in June and January.  I am not sure whether this is wise.  Shouldn't we just use C tzname is it is available?

I don't think tzname is really all that useful. In mxDateTime,
I use strftime() with "%Z" to obtain the timezone string for
a given local time.

tzname tries to identify non-DST vs. DST of the local time zone,
but this may fail for cases where a country switches DST settings
in a particular year as it happened in Russia:

https://www.timeanddate.com/time/zone/russia/moscow