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I have reorganized the commits in a branch before it is going to be made public causing the timestamps of the commits to be in an mixed up order. I would rather have them be all be today with only seconds in between.

Obviously these time stamps won't be correct either, but since this is the time when things go public I prefer that over a mixed up history, time-wise.

So how do I tell git to create new timestamps while rebasing?

phs
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tarsius
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    With Git 2.29 (Q4 2020), a `git rebase --root` or `-i`, with `--reset-author-date` will work. See [my answer below](https://stackoverflow.com/a/63751470/6309) – VonC Sep 05 '20 at 07:26

4 Answers4

179

Use --ignore-date:

git rebase --ignore-date
Dávid Horváth
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Michael Krelin - hacker
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  • I believed to remember that it involved setting some envvar. (Actually I did check for that in the manpage but did not find anything. But I did not go through the options, because I was so certain it involved a envvar.) – tarsius Oct 16 '09 at 19:20
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    tarsius, I think you're talking about `git filter-branch`, but you don't really need it for a simple task like this. – Michael Krelin - hacker Oct 16 '09 at 19:24
  • Well actually it does not work with git from the master branch: git rebase -i --ignore-date a7a86fe error: unknown option `ignore-date' This seams to be a bug however: in the manpage this option actually is listed. – tarsius Oct 16 '09 at 19:27
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    I have tried it before posting.. Except for I haven't done it interactively, maybe that's the trick? Also, have you tried the --committer-date-is-author-date alias? Maybe the --ignore-date was introduced in later version, I have no idea. – Michael Krelin - hacker Oct 16 '09 at 20:06
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    Yes, if done non-interactively it works. But then - as always with rebase - the very first commit is not affected. – tarsius Feb 27 '10 at 21:18
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    @MichaelKrelin-hacker: according to the documentation, _--ignore-date These flags are passed to git am to easily change the dates of the rebased commits (see git-am[1]). Incompatible with the --interactive option._ – Tim Nov 25 '15 at 21:35
  • @tarsius: the given commit SHA1 is the parent commit your editing the children from. You need such a basis to get the work done. You can't cut off the branch you're sitting on :) – Tim Nov 25 '15 at 21:38
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    @MichaelKrelin-hacker What you can do is first `git rebase --ignore-date` to update _author dates_ then `git rebase -i` to reorder/modify commits. – Tim Nov 25 '15 at 21:42
  • @Tim, absolutely, though it wasn't me who needed that. Thanks for pointing that out in the docs though! – Michael Krelin - hacker Nov 25 '15 at 22:09
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    @Tim The root commit does not have a parent, and when I asked this question I also wanted to change the date of that commit. Now we have `--root`, which makes this possible. – tarsius Nov 26 '15 at 01:24
  • @tarsius, hey, thanks for telling, I didn't know about `--root`. Not that I immediately need it, but it's good to know. – Michael Krelin - hacker Nov 26 '15 at 07:14
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    `Incompatible with the --interactive option.` [See docs](https://git-scm.com/docs/git-rebase#git-rebase---ignore-date) – Vlastimil Ovčáčík Jun 09 '17 at 12:48
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    @MichaelKrelin-hacker yeah :) I didn't notice it at first, so I made this eye catching comment and upvoted him. – Vlastimil Ovčáčík Jun 11 '17 at 13:52
  • I tried `--reset-author-date` together with `-i` and it worked perfectly! – AlikElzin-kilaka Apr 12 '21 at 04:18
32

There are the following ways

  1. Normal rebase

    git rebase --ignore-date

  2. Interactive rebase

    git rebase -i master
git commit --amend --date=now
git push origin <branch> -f
Umar Asghar
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  • Thank god for an easy-to-understand way to do the job for any kind of rebase! Thank you! I will use `--date=new` _every_ time I use `--amend` from now on. IMO, any `squash` or `fixup` in an interactive rebase and any `commit --amend` should automatically update the timestamp _now_ or at least to the date of the most recent of the combined commits. I don't think it can reasonably be argued that the combined commit should have the same timestamp as the first of the commits being combined, as though nothing had changed since then, and yet that's what we have today. – Pablo Halpern Feb 05 '21 at 16:34
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In my case rebasing changed timestamps to CommitDate value, so in gitweb a bunch of months old commits showed up as 4 days old. I found the last commit with the correct date and did:

$ git rebase --committer-date-is-author-date SHA
lkraav
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    No, it's not. In fact, it's the exact opposite. From the docs of [`git rebase`](https://git-scm.com/docs/git-rebase): "_These flags are passed to `git am` to easily change the dates of the rebased commits_". In [`git am`](https://git-scm.com/docs/git-am) it says: `--committer-date-is-author-date` "_[...]allows the user to lie about the committer date by using the same value as the author date_" while `--ignore-date` "_[...]allows the user to lie about the author date by using the same value as the committer date_". – Enrico Campidoglio Feb 18 '16 at 22:28
14

From comments:

Incompatible with the --interactive option

Actually... it is no longer incompatible with Git 2.29 (Q4 2020): "git rebase -i"(man) learns a bit more options.
Options which are compatible with:

  • --interactive/-i
  • --root!

See commit 6160b2e (26 Aug 2020) by Junio C Hamano (gitster).
See commit 2712669 (17 Aug 2020), and commit ef484ad (13 Jul 2020) by Rohit Ashiwal (r1walz).
See commit a3894aa, commit 7573cec, commit e8cbe21 (17 Aug 2020) by Phillip Wood (phillipwood).
(Merged by Junio C Hamano -- gitster -- in commit 9c31b19, 03 Sep 2020)

rebase -i: support --ignore-date

Original-patch-by: Rohit Ashiwal
Signed-off-by: Phillip Wood

Rebase is implemented with two different backends - 'apply' and 'merge' each of which support a different set of options.

In particular the apply backend supports a number of options implemented by 'git am(man)' that are not implemented in the merge backend.
This means that the available options are different depending on which backend is used which is confusing.

This patch adds support for the --ignore-date option to the merge backend.

This option uses the current time as the author date rather than reusing the original author date when rewriting commits.
We take care to handle the combination of --ignore-date and --committer-date-is-author-date in the same way as the apply backend.

And:

rebase: add --reset-author-date

Helped-by: Junio C Hamano
Signed-off-by: Rohit Ashiwal

The previous commit introduced --ignore-date flag to rebase -i, but the name is rather vague as it does not say whether the author date or the committer date is ignored.
Add an alias to convey the precise purpose.

--reset-author-date

Also:

rebase -i: support --committer-date-is-author-date

Original-patch-by: Rohit Ashiwal
Signed-off-by: Phillip Wood

This patch adds support for the --committer-date-is-author-date option to the merge backend.
This option uses the author date of the commit that is being rewritten as the committer date when the new commit is created.

git rebase now includes in its man page:

--committer-date-is-author-date:

Instead of using the current time as the committer date, use the author date of the commit being rebased as the committer date.
This option implies --force-rebase.

git rebase also includes in its man page:

--ignore-date:

This flag is passed to 'git am' to change the author date of each rebased commit (see git am).

Note that in 2.29 (above), "--committer-date-is-author-date" option of "rebase" and "am" subcommands lost the e-mail address by mistake, which has been corrected with Git 2.29.1 (Q4 2020).

See commit 5f35edd, commit 16b0bb9, commit 56706db (23 Oct 2020) by Jeff King (peff).
(Merged by Junio C Hamano -- gitster -- in commit f34687d, 26 Oct 2020)

am: fix broken email with --committer-date-is-author-date

Signed-off-by: Jeff King

Commit e8cbe2118a (am: stop exporting GIT_COMMITTER_DATE, 2020-08-17) rewrote the code for setting the committer date to use fmt_ident(), rather than setting an environment variable and letting commit_tree() handle it.
But it introduced two bugs:

  • we use the author email string instead of the committer email
  • when parsing the committer ident, we used the wrong variable to compute the length of the email, resulting in it always being a zero-length string

This commit fixes both, which causes our test of this option via the rebase "apply" backend to now succeed.

And:

rebase: fix broken email with --committer-date-is-author-date

Reported-by: VenomVendor
Signed-off-by: Jeff King

Commit 7573cec52c ("rebase -i: support --committer-date-is-author-date", 2020-08-17, Git v2.29.0-rc0 -- merge listed in batch #13) copied the committer ident-parsing code from builtin/am.c.
And in doing so, it copied a bug in which we always set the email to an empty string.

We fixed the version in git-am in the previous commit; this commit fixes the copied code.

VonC
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