Update git commit author date when amending

You can change the author date with the --date parameter to git commit. So, if you want to amend the last commit, and update its author date to the current date and time, you can do:

git commit --amend --date="$(date -R)"

(The -R parameter to date tells it to output the date in RFC 2822 format. This is one of the date formats understood by git commit.)

Another way to do this is

git commit --amend --reset-author

This does change the commit author as well as the date - but if it was originally your unpushed commit then that's a no-op.

You can also add --no-edit if you want to update the date on multiple commits but you want the commit messages to stay untouched. This way you will not be prompted to edit the message for each commit.

I like Mark's answer and used it myself several times, but now I'm on OS X and date -R is not supported. But everything is much easier than original answer made us think, just use empty string!

git commit --date= --amend

UPDATE:

You can also try

git commit --date="$(date)" --amend

Or in new versions of git

git commit --date=now --amend

As of Git v2.1.4 (tested on Debian 8 (Jessie))

git commit --amend --date=now