[plt-scheme] no prehistoric dates?

At Wed, 18 Feb 2009 13:22:33 -0800, YC wrote:
> make-date cannot handle negative years, i.e. no BC time.
> 
> > (make-date 0 0 0 1 1 -1 0 0 #f 0)
> make-date: expected argument of type <nonnegative exact integer>; given
> -1
> 
> Is there a reason for such restriction?

None that I can see, so I'll change the `date' structure type to allow
it.