Zope time zone setting

I'm trying to set the TZ on a zope5.9 instance, someting like TZ America/Los_Angeles. I did try to set it in buildout.cfg and in zope.conf without any success. Can you please give mi some hint? Thanks a lot

Zope has little to do with the timezone. What effect to you expect
from setting the timezone?

Zope uses DateTime as some places; this uses the timezone information
from Python's time module. Read its documentation to learn
how to influence the timezone used by Python
(one way is to set the TZ environment variable).