How to change your git commit date after the facts

Change lastmod for Hugo when lastmod is based on git commit

stackoverflow - re-write git commit time

git filter-branch -f --env-filter \
    'if [ $GIT_COMMIT = 9fb407b47803c201725fd02c1a7406c93e5cad42 ]
     then
         export GIT_AUTHOR_DATE="Sun May 10 00:00:00 2020 +0900"
         export GIT_COMMITTER_DATE="Sun May 10 01:00:00 2020 +0900"
     fi'

Don’t forget to use –force when pushing upstream.