How can one change the timestamp of an old commit in Git?

Question

The answers to How to modify existing, unpushed commits? describe a way to amend previous commit messages that haven\'t yet been pushed upstream. The new messages inherit t

Answer 1

Set the date of the last commit to the current date

GIT_COMMITTER_DATE="$(date)" git commit --amend --no-edit --date "$(date)"

Set the date of the last commit to an arbitrary date

GIT_COMMITTER_DATE="Mon 20 Aug 2018 20:19:19 BST" git commit --amend --no-edit --date "Mon 20 Aug 2018 20:19:19 BST"

Set the date of an arbitrary commit to an arbitrary or current date

Rebase to before said commit and stop for amendment:

1. git rebase <commit-hash>^ -i
2. Replace pick with e (edit) on the line with that commit (the first one)
3. quit the editor (ESC followed by :wq in VIM)
4. Either:

• GIT_COMMITTER_DATE="$(date)" git commit --amend --no-edit --date "$(date)"
• GIT_COMMITTER_DATE="Mon 20 Aug 2018 20:19:19 BST" git commit --amend --no-edit --date "Mon 20 Aug 2018 20:19:19 BST"

Source: https://codewithhugo.com/change-the-date-of-a-git-commit/

Answer 2

After reading all the answers I came up with a more succinct and convenient way of editing the date of multiple commits at once without the need of rebasing interactively:

git rebase HEAD~4 --exec "git commit --amend --no-edit --date 'now'"

It changes both the committer and author dates.

Answer 3

Here is a convenient alias that changes both commit and author times of the last commit to a time accepted by date --date:

[alias]
    cd = "!d=\"$(date -d \"$1\")\" && shift && GIT_COMMITTER_DATE=\"$d\" \
            git commit --amend --date \"$d\""

Usage: git cd <date_arg>

Examples:

git cd now  # update the last commit time to current time
git cd '1 hour ago'  # set time to 1 hour ago

Edit: Here is a more-automated version which checks that the index is clean (no uncommitted changes) and reuses the last commit message, or fails otherwise (fool-proof):

[alias]
    cd = "!d=\"$(date -d \"$1\")\" && shift && \
        git diff-index --cached --quiet HEAD --ignore-submodules -- && \
        GIT_COMMITTER_DATE=\"$d\" git commit --amend -C HEAD --date \"$d\"" \
        || echo >&2 "error: date change failed: index not clean!"