I started writing an Olson timezone querying program (to replace DT:TZ:Catalog), and discovered that DT:TZ:Tzfile declares that the current offset in the Africa/Cairo zone is unknown. This is due to a problem in the tzfile itself, caused by a bug in zic. It only shows up in careful use of the 64-bit version of the file, which is exactly what DT:TZ:Tzfile does. I'm treating this as a showstopper for replacing DT:TZ. I've reported the problem to the Olson folks.
-zefram
