FW: Longitude/Latitude to TIME zone

[Alex LIVINGSTON]

>I'm sorry, but this just not true, and is very misleading.

I assumed that Muhammad would be aware of the fact that real-life land time
zones do not stick to exact formulaic boundaries (or would have at least
suspected it - one glance at a time-zone map would have confirmed it) and
that his query implied idealized conditions. Indeed, his mention of
"heading" suggested to me that he might have been at sea, so to speak (no
pun intended), where the "time zone" can be idealized. My "formula" for
determining whole-hour time zone is, I believe, generally applied on the
open ocean.

>Longitude is, at best, only a /very/ broad indicator of the time zone. If
>your message was true, then you (in Australia) would not have the
>Broken Hill situation, and SA & NT would be on +9 (and not +8:30).

Actually, it's +9:30 (SA, NT and Broken Hill), and +10:30 in SA and Broken
Hill in "summer", and "if my message was true" the +9 zone would extend
1&1/2 degrees west of WA's eastern border and 1&1/2 degrees east of NSW's
western border (and 4&1/2 degrees east of the NT/Queensland border).

(I might add that I am not proud of the time-zone chaos in Australia, which
is responsible for no fewer than four off-hour time offsets which are, at
best, only very flimsily justifiable.)

>The actual pattern of time zones is fundamentally based on countries and
>provinces. In fact, in real-life time zone terms, I think that I
>would go so far as to say that the 15 degree boundaries serve no useful
>purpose whatsoever.

I quite agree. In fact time zones are often based on even smaller regions
than provinces.

>Best wishes
>Alan Pritchard
>The GLOBAL GAZETTEER: the world on file
>http://www.allm-geodata.com
>Tel: +44 (0) 1202 417 477

I could perhaps have averted your complaint by pointing out at the end of
my message that, of course, actual, on-land time "zones" (in quotation
marks because it is a somewhat misleading and ambiguous term) are subject
to local jurisdiction.

Cheers,

Alex


PS: I nearly didn't cc this to Muhammed, because the first message I sent
to him bounced back indicating "host unknown". He thus hasn't heard
anything from me yet (and may never).

>
>> > -----Original Message-----
>> > From:	Muhammad Safeer [SMTP:msafeer at khi.compol.com]
>> > Sent:	Thursday, June 01, 2000 7:47 AM
>> > To:	tz at elsie.nci.nih.gov
>> > Subject:	Longitute/Latitute to TIME zone
>> >
>> > Is there any formula to convert Longitute/Heading to time zone.
>> >
>> > Regards.
>> >
>> > Muhammad Safeer.
>>
>> Muhammad,
>>
>> I'm not sure what "heading" has to do with it. Is that the direction in
>> which travel is proceeding? If so, it doesn't affect your "time zone".
>> Only
>> longitude affects that. You can calculate your actual mean-solar-time
>> offset from Greenwich in hours simply by dividing your longtude in
>> degrees
>> by 15. For longitudes east the answer is in hours ahead of Greenwich and
>> for longitudes west the answer is in hours behind Greenwich. If you
>> want to
>> calculate the nearest whole-hour time zone offset, you can simply round
>> the
>> answer from the previous calculation to the nearest hour. For example, I
>> live and work at longitude 151 degrees and about 15 minutes east. That
>> means the time by the sun here is 10 hours and about 5 minutes ahead of
>> Greenwich. The nearest whole-hour time zone offset is thus 10 hours
>> ahead
>> of Greenwich.
>>
>> --Alex
>>
>> _______________
>> Alex LIVINGSTON
>> Macintosh and Lotus Notes Support / Information Technology (IT)
>> Australian Graduate School of Management (AGSM)
>> UNSW SYDNEY NSW 2052 / Australia
>>
>> Facsimile: +61 2 9931-9349 / Telephone: +61 2 9931-9264
>> Time     : UTC+11---[last Mar. Sun.---UTC+10---[last Aug.
>> Sun.---UTC+11---
>>
>> At midday today, Friday, June 2,
>>   time since epoch (1-1-1 at 00:00:00) is
>>     730272.5 days = 1999.41819476 average Gregorian years
>>   time until 3rd millennium, 21st century, 201st decade, 2001st year is
>>     212.5 days = .58180524 average Gregorian years
>>
>>


_______________
Alex LIVINGSTON
Macintosh and Lotus Notes Support / Information Technology (IT)
Australian Graduate School of Management (AGSM)
UNSW SYDNEY NSW 2052 / Australia

Facsimile: +61 2 9931-9349 / Telephone: +61 2 9931-9264
Time     : UTC+11---[last Mar. Sun.---UTC+10---[last Aug. Sun.---UTC+11---

At midday today, Tuesday, June 6,
  time since epoch (1-1-1 at 00:00:00) is
    730276.5 days = 1999.42914639 average Gregorian years
  time until 3rd millennium, 21st century, 201st decade, 2001st year is
    208.5 days = .57085361 average Gregorian years