This behaviour is a side effect of moving the /usr/share/zoneinfo/UTC to tzdata-legacy. We could move this file back to quickly unbreak the autopkgtest.
The better solution is to set TZ=UTC0 instead of TZ=UTC because UTC0 is defined to be available on all systems even with an empty /usr/share/zoneinfo.
I verified that the output of bug.c is correct with tzdata 2023c-8ubuntu1 and without tzdata-legacy when changing to TZ=UTC0.
This behaviour is a side effect of moving the /usr/share/ zoneinfo/ UTC to tzdata-legacy. We could move this file back to quickly unbreak the autopkgtest.
The better solution is to set TZ=UTC0 instead of TZ=UTC because UTC0 is defined to be available on all systems even with an empty /usr/share/ zoneinfo.
I verified that the output of bug.c is correct with tzdata 2023c-8ubuntu1 and without tzdata-legacy when changing to TZ=UTC0.
See also https:/ /bugs.debian. org/cgi- bin/bugreport. cgi?bug= 1043250