[tz] On merging timezones - a radical proposal.

Clive D.W. Feather clive at davros.org
Thu May 23 13:31:03 UTC 2013

random832 at 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 at davros.org     | it will get its revenge.
Web: http://www.davros.org  |   - Henry Spencer
Mobile: +44 7973 377646

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