These codes tested in macOS and Linux both In windows you need regkey | cmd /c /v | or set command to replace export in UNIX terminal
Another things that important are the ENVs : GIT_COMMITTER_DATE and GIT_AUTHOR_DATE that need to be set before you commit your changes
If you want only change date with not any change at all add --no-edit
to your command
These codes for Linux and macOS
export GIT_COMMITTER_DATE="Wed Jan 1 14:55:00 2015 +0100"
git commit --amend --date "Wed Jan 1 14:55:00 2015 +0100" -m 'fix committer_date and author_date'
unset GIT_COMMITTER_DATE
export GIT_COMMITTER_DATE="2015-01-01 14:55:00 +0100"
git commit --amend --date "2015-01-01 14:55:00 +0100" -m 'fix committer_date and author_date'
unset GIT_COMMITTER_DATE
With no changes at all
export GIT_COMMITTER_DATE="Wed Jan 1 14:55:00 2015 +0100"
git commit --amend --no-edit --date "Wed Jan 1 14:55:00 2015 +0100" -m 'fix committer_date and author_date'
unset GIT_COMMITTER_DATE
export GIT_AUTHOR_DATE="2015-01-01 14:55:00 +0100"
git commit --amend --no-edit --date "2015-01-01 14:55:00 +0100" -m 'fix committer_date and author_date'
unset GIT_AUTHOR_DATE