The different time zones might be an issue. dom0 / Templates are “normal” but Qubes-Whonix templates are in UTC.
For Debian 11 / bullseye in sdwdate a change was required (and introduced since the first Debian 11 based Whonix version 16) to set in python:
os.environ["LC_TIME"] = "C"
os.environ["TZ"] = "UTC"
time.tzset()
This python change may need to be added to any Qubes source code. For example the python based Qubes dom0 file /etc/qubes-rpc/qubes.GetDate might need it.
Furthermore, to improve the robustness (and perhaps even fix this bug) any invocation of date should be prefixed with --utc, i.e. date --utc for any Qubes shell/bash scripts.
Internally, programmatically Qubes should always handle time in UTC. The time shown to the user when manually running date or looking at the systray can remain as is in user local timezone, no problme.