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

Building on theosp's answer, I wrote a script called git-cdc (for change date commit) that I put in my PATH.

The name is important: git-xxx anywhere in your PATH allows you to type:

git xxx
# here
git cdc ... 

That script is in bash, even on Windows (since Git will be calling it from its msys environment)

#!/bin/bash
# commit
# date YYYY-mm-dd HH:MM:SS

commit="$1" datecal="$2"
temp_branch="temp-rebasing-branch"
current_branch="$(git rev-parse --abbrev-ref HEAD)"

date_timestamp=$(date -d "$datecal" +%s)
date_r=$(date -R -d "$datecal")

if [[ -z "$commit" ]]; then
    exit 0
fi

git checkout -b "$temp_branch" "$commit"
GIT_COMMITTER_DATE="$date_timestamp" GIT_AUTHOR_DATE="$date_timestamp" git commit --amend --no-edit --date "$date_r"
git checkout "$current_branch"
git rebase  --autostash --committer-date-is-author-date "$commit" --onto "$temp_branch"
git branch -d "$temp_branch"

With that, you can type:

git cdc @~ "2014-07-04 20:32:45"

That would reset author/commit date of the commit before HEAD (@~) to the specified date.

git cdc @~ "2 days ago"

That would reset author/commit date of the commit before HEAD (@~) to the same hour, but 2 days ago.

---

Ilya Semenov mentions in the comments:

For OS X you may also install GNU coreutils (brew install coreutils), add it to PATH (PATH="/usr/local/opt/coreutils/libexec/gnubin:$PATH") and then use "2 days ago" syntax.