To commit in the past...you need to be creative and get a repo where you can commit to.
$ export GIT_AUTHOR_DATE="Sat, 28 Mar 2015 22:00:00 -0700"
$ export GIT_COMMIT_DATE="Sat, 28 Mar 2015 22:00:00 -0700"
$ git commit -m "commit in the past"
Save those github streaks when you're off by only a few minutes.