DST incorrectly ends on October 1st instead of October 25th
This appears to be a regression in glib 2.66. If my bisecting was correct, it started with commit 25d950b6.
01/Oct/2020:07:00:00 +0200 (Eastern European Time).
With glib 2.64 it correctly shows
... +0300 (Eastern European Summer Time).
What's interesting is that glib 2.66 works fine with tzdata 2020a installed. I believe the following code change in tzdata 2020b is related:
zic now defaults to '-b slim' instead of to '-b fat'
The issue also manifests in Xfce's panel clock which is one hour behind the current time. It gets the time from