Eli Zaretskii <eliz@gnu.org> writes:

> My vote is to drop the requirement.  With all the possible cases which
> Git supports of getting a commit into the upstream repository, I don't
> think we can guarantee monotonous dates anyway.

On top of that, Git already provides monotonous dates (assuming no
deliberate effort to make them non-monotonous) on commits in the
'CommitDate' field.  (Parts of) Git already assume(s) such a monotonous
timestamps:

       --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.

               Warning
               The history walking machinery assumes that commits have
               non-decreasing commit timestamps. You should consider if
               you really need to use this option. Then you should only
               use this option to override the committer date when
               rebasing commits on top of a base which commit is older
               (in terms of the commit date) than the oldest commit you
               are applying (in terms of the author date).
  -- git-rebase(1)

See also 'git log --format=fuller'.
-- 
Arsen Arsenović