What is a time zone?
alex at agsm.edu.au
Fri Feb 16 06:27:45 UTC 2001
At 14:43 +0000 2001-02-15, Clive D.W. Feather wrote:
>David Keegel said:
>> I think common usage outside this group is that a time zone has variable
>> boundaries, and is something like the set of places which *currently*
>> observe the same time (although perhaps US EST and CDT might be
>> considered different time zones).
>Change this to say "currently observe the same time and intend to do so for
>the indefinite future" and you eliminate that problem.
I presume by "the same time" Clive means "the same time as each
other" and not necessarily the same UT offset. That would mean that
Queensland would have to be considered as a separate time zone from
the other mainland Australian eastern states (and territory), and,
under the regimen that applied until 1999 and will possibly continue
this year, Tasmania as yet another. The Northern Territory and South
Australia would also have to be considered as separate from each
other. I don't know whether Australians would see it that way in
general. They might concede that they are different time zones while
they are observing different times, but I doubt they would otherwise.
I assume David is thinking of Indiana, most of which is on the same
time as the US central zone during "summer", but is still thought of,
by many, as being in the eastern time zone. Instead of doing that,
and ignoring Clive's amendment, one could think of the time zone
boundary as changing twice a year. The difficulty with that, of
course, is that, under one interpretation of such a scenario, (most
of) Indiana would change time zone twice a year even though its
clocks don't change.
The alternative (which seems far superior to me and is consistent
with labelling time zones with their offset alone) is to think of
Indiana as remaining in the same zone, the boundaries of which move
east and west around it in an annual cycle. This accords better with
what I imagine is the general Australian perception of a time zone.
The North American perception is harder to sustain in Australia,
where more than half the country in areal terms (but less than half
in population terms) does not observe daylight-saving time. The
geographically-based designations "Eastern Time" (ET) and "Central
Time" (CT), each meaning whatever the time being observed in its
respective zone is on the date in question, cannot be made to work in
Australia. Even in North America, in order for them to work
universally, most of Indiana, and parts of Canada, _would_ have to be
thought of as swapping between the two zones twice a year!
I am flabbergasted at the resistance there seems to be to the idea of
people knowing what their local offset(s) from UTC is/are. In the
vast majority of cases such an offset is a one- or two-digit number
with a sign, and nowhere is there a need to know more than two of
these, in a world of 8-, 9-, and 10-digit phone numbers and post
codes, not to mention PINs and (in the US at least) social security
numbers! In a place where daylight saving is practised, it is simply
a matter of knowing these two simple numbers (like one's floor,
house, apartment, and/or room number) and knowing which one applies
at the time, which is simply a matter of knowing whether daylight
saving is in force or not.
Can't we time-zone whizzes (if I may be so bold as to include myself)
allow ourselves to have a tiny bit of conscious influence, rather
than (or as well as to start with) bending over backwards to
accommodate the whims and follies of the powers that be? We are doing
the world a significant favor (aren't we?); it doesn't seem too
audacious to make it known what would make it easier for us to
continue to do so, especially if the general population would also
benefit (we think). Should we be deterred just because the resistance
seems almost insurmountable? Would it inevitably threaten our
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