BUG #16697: timetz regression test seems to have a false failure

The following bug has been logged on the website:

Bug reference:      16697
Logged by:          Russel Kubes
Email address:      russkubes@yahoo.com
PostgreSQL version: 12.4
Operating system:   Linux debian-vm 4.19.0-12-amd64 #1 SMP Debian 4.19
Description:

While building Postgres 12.4 from source today on two different machines,
the "timetz" test has failed. When reviewing the "diff" file, it looks like
the only reason they failed is a differing UTC offset after a query that
looks like the UTC offset isn't really relevant. I've built 12.4 a few times
before on each machine and did not run into this issue. It started today,
which makes me wonder if it has something to do with Daylight Saving Time.

I feel confident that I can ignore this error. However, I wanted to pass it
along just in case someone can determine whether this is a minor issue in
the regression test, or if there's a potential edge case issue in the actual
Postgresql code.

The output of the "regression.diffs" file is pasted below:

diff -U3
./postgres/obj/../postgresql-12.4/src/test/regress/expected/timetz.out
./postgres/obj/src/test/regress/results/timetz.out
---
./postgres/obj/../postgresql-12.4/src/test/regress/expected/timetz.out    2020-08-10
17:15:53.000000000 -0400
+++ ./postgres/obj/src/test/regress/results/timetz.out    2020-11-02
20:35:14.681128516 -0500
@@ -94,25 +94,25 @@
 SELECT '23:59:59.999999'::timetz;
        timetz       
 --------------------
- 23:59:59.999999-07
+ 23:59:59.999999-08
 (1 row)
 
 SELECT '23:59:59.9999999'::timetz;  -- rounds up
    timetz    
 -------------
- 24:00:00-07
+ 24:00:00-08
 (1 row)
 
 SELECT '23:59:60'::timetz;  -- rounds up
    timetz    
 -------------
- 24:00:00-07
+ 24:00:00-08
 (1 row)
 
 SELECT '24:00:00'::timetz;  -- allowed
    timetz    
 -------------
- 24:00:00-07
+ 24:00:00-08
 (1 row)
 
 SELECT '24:00:00.01'::timetz;  -- not allowed