On Thu, Sep 18, 2008 at 4:56 PM, Joseph Wright <[log in to unmask]> wrote: >> Something like >> \IfOldPackageDate{2006/06/08}{...implement old functionality...} >> ) > > An interesting idea, but gets very complex very quickly (if one makes > more than a trivial number of changes). True. Perhaps a better idea, for those interested in absolute backwards compatibility, is a (standard) method to keep the old package versions lying around with standardised filenames (say, siunitx-20080823.sty) that can be loaded when necessary. Lance Carnes wrote about this sort of thing in an editorial in the most recent PracTeX Journal. So I guess there must be *some* need for it... Will