It would be nice with an Interface (Java speak) that could be implemented for different countries. Dates, telephone numbers, addresses, holidays, sorting are general things. Postal codes that maps to regions and cities may also be a general thing. But our Swedish "personnummer" (personal number) is not a thing that exists everywhere. So the base class could list the general things and lett every country module add it's own special methods.

And, as Hanamaki wrote, namespace needs to be worked out.

Anyone know if a project like this exists for other languages? How about Python?