Git rebase and create new timestamps (dates)

$ git checkout development
$ git rebase --ignore-date origin/developmentCopy

what --ignore-date does:

Instead of using the author date of the original commit, use the current time as the author date of the rebased commit.

The opposite is the --committer-date-is-author-date option, which is the default, in my system:

Instead of using the current time as the committer date, use the author date of the commit being rebased as the committer date.