Keyboard layouts, sort orders, paper size, and unit defaults are among the
things that might be different between System Software versions.
Inside Macintosh, Volume I, Chapter 19, and Volume 5, Chapter 16 (available in
omnibus edition from Addison Wesley, ISBN #0-201-17737-4) discusses the
International Utilities Package that allows software developers to make their
software country-independent.
Everything you need to know about localization should be contained in these
documents.