FATAL: invalid value for parameter "TimeZone" after upgrade from 9.2 to 9.6

Good morning.

My issue is more or less similar to
http://www.postgresql-archive.org/Upgrading-from-PG-8-3-3-to-9-3-4-FATAL-invalid-value-for-parameter-quot-TimeZone-quot-quot-PST-quot-td5805665.html

However what I'm looking to answer is why this wasn't fatal in 9.2? From
that other thread, it seems like the change occurred in 9.3, and in the 9.3
release notes I see this:

Sync our copy of the timezone library with IANA release tzcode2017c (Tom
> Lane)
>

> This fixes various issues; the only one likely to be user-visible is that
> the default DST rules for a POSIX-style zone name, if no posixrules file
> exists in the timezone data directory, now match current US law rather than
> what it was a dozen years ago.

Would this explain why the app server was able to connect with
timezone='CST' (in my case) in 9.2 but not in 9.6? Our workaround was
either to use CST6CDT or just not set it altogether (which is what we chose
since we're always in US/Central).

For what it's worth this is on CentOS 6.

Don.

--
Don Seiler
www.seiler.us