Junio C Hamano <gitster@xxxxxxxxx> writes: >> +test_expect_success 'commit date shows timezone offset +0000 when user.hideTimezone is true and reset' ' >> + git config user.hideTimezone true && >> + git commit --amend --reset-author && >> + git log -1 > output && >> + grep "Date: .* +0000" output > > This one IS interesting, but keep the GIT_AUTHOR_DATE set and > exported. As long as that is from a timezone different from UTC, we > are testing what we want to test here. Note. Once GIT_AUTHOR_DATE and friends are set fully including timezone, we won't even read TZ because there is no need to. But you can do something along these lines: test_config user.hideTimeZone true && ( export GIT_AUTHOR_DATE=@1600000000 TZ=UTC-09 && git commit ... && git show -s --format='%aI' >output && echo 2020-09-13T15:26:40+03:00 >expect && ... I think (haven't actually tested) "git commit --date=<datestring>" option is handled the same way, i.e. comparing these two would be a way not to touch the environment variable. TZ=UTC-09 git commit --date=@1600000000 ... && TZ=UTC-09 git -c user.hideTimeZone=true commit --date=@1600000000 ... && git show -s --format='%aI' HEAD~1 >output0 && git show -s --format='%aI' HEAD~0 >output1