For those using Powershell
git rebase DESIRED_REF^ -i
$commitDateString = "2020-01-22T22:22:22"
$env:GIT_COMMITTER_DATE = $commitDateString
git commit --amend --date $commitDateString
$env:GIT_COMMITTER_DATE = ""
git rebase --continue
Credit to https://mnaoumov.wordpress.com/2012/09/23/git-change-date-of-commit/