Back-dating commits--way back--for constitution.git

["Joel C. Salomon" <joelcsalomon@gmail.com>]

I'd figured to play with Git in an unusual way: to create a repository
for the U.S. Constitution where amendments are presented as patches.
E.g., instead of the First Amendment being placed at the end (as is
usual) I'm putting it in Article 1, Section 9 (Limitations of Congress).
 Proposed amendments get branches, which get merged in later.

But I'm trying to get the dates right, and I'm missing something.  For
example, I made the initial commit with the line

	$ git commit --author="The Philadelphia Convention <>" \
	 --date="Mon, 17 Sep 1787 12:00:00 EST"

but that's not actually setting the commit date to 1787.

Am I doing something wrong, or is Git (quite reasonably) unable to
accept commit dates that far in the past?

--Joel