random832@fastmail.us said:
Why do we have zones that track _cities'_ movements from one timezone to another?
We don't. We *define* a timezone as being a geographical area where all the clocks should always show the same time since 1970. Therefore a city *never* moves from one timezone to another. If a geographical area should have clocks showing different times in (say) April 1996, then that area contains more than one time zone. We do *NOT* use "timezone" to refer to *concepts* like "Eastern Standard Time" or "British Summer Time"; let alone "North American Eastern Time". (I think we have GMT+/-N zones, but that's because they are used at sea and so have geographic meaning.) We could add such zones, but these would be *additional* timezones. A city would not move from the NACT zone to the NAET zone; rather, it remains in its own zone, which shows the same time as NACT before the transition date and the same time as NAET after it. -- Clive D.W. Feather | If you lie to the compiler, Email: clive@davros.org | it will get its revenge. Web: http://www.davros.org | - Henry Spencer Mobile: +44 7973 377646