At the Science of Time Symposium in Cambridge Massachussetts earlier this year Kevin Birth showed a situation that tz does not have to handle. http://gallica.bnf.fr/ark:/12148/btv1b8490533n gives a view of one surviving example of the 1589 Vergleichung nachvolgender siben Uhren This was a chart to translate between the 7 different ways of counting hours (some employing unequal hours) which visitors might know from their home cities (and their pocket sundials) and the hours which were in use by various different clock towers and agencies in Nuremberg. -- Steve Allen <sla@ucolick.org> WGS-84 (GPS) UCO/Lick Observatory--ISB 260 Natural Sciences II, Room 165 Lat +36.99855 1156 High Street Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 http://www.ucolick.org/~sla/ Hgt +250 m