A simple proposal to move forward from where we are with reliable new rules: 1) Each inhabited ISO-3166 region must have at least one fully defined zone (LMT, pre and post 1970) 2) Links must not cross ISO-3166 region bouindaries Some of the rules that would require reworking (not a complete list): Europe/Busingen America/Atikotan America/Aruba America/Anguilla America/Port_of_Spain Europe/Zagreb Europe/Vatican Note that America/Montreal does not require reworking as a result of the first two new rules, although since it looks to have detailed historical information it would be unwise to lose that. Therefore I would add a third rule: 3) Existing pre-1970 data shall be respected If accepted, then these rules would be encoded in the theory file. Stephen