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73416ba
(Get the code!)
According to Wikipedia there are 245 political entities in the world...
http://
... and only 193 with general international recognition....
So we've got 24 time zones...
A little history:
In 1878, Sir Sandford Fleming (1827–1915) developed the system of worldwide time zones that we still use today. He proposed that the world be divided into 24 time zones, each spaced 15º (fifteen degrees) of longitude apart (like 24 sections of an orange). He came to this idea because Earth completes a rotation every 24 hours and there are 360º of longitude, so each hour Earth rotates 1/24th of a circle or 15º.
So if this is the logic... why not just define each 24 hr time period... based on it's longitude...
Then define "political" exemptions which to the best of my research cover large geographical terroritories but are clearly defined by geo-political boundaries...
China is ONE timezone.
A few US States don't do timezones..
.Alaska (USA) should span a few timezones, but has been consolidated to 1.
And here's the current info on daylight savings time:
http://
Taking a look at this "large" problem and breaking it down to the most general concrete information and then defining exemptions .. has me looking at it this way...
1. define "true" time zones as represented by the only data we know to be consistant... Longitude.
-- The location of the user is always technically based on Longitude and Latitude... so this way we should be able to determine the "true" timezone.
2. define continental and sub-continental exemptions
-- define large exceptions... exemptions that span countries...
-- maybe this never happens
3. define country-wide timezones
-- basically which countries wrap themselves into a single timezone.
--- China
4. define regional exemptions
-- a regional exemption must fit inside of a country
--- aka alaska, usa
--- Navajo tribal nation
---- spans 3 states and participates in daylight savings time even though part of the nation lies in Arizona which does not participate.
--- Russia, 11 time-zones
---- permanent daylight savings time (so 1hr ahead of actual time zone)
--- other exemptions are the half and quarter-time modifications
5. unique / specific cirumstances...
In South Asia, if you follow a straight line west along the 27º latitude you will move back and forth across time zones: from Pakistan UTC +5 hours, India +5:30, Nepal +5:45, India (Sikkim) +5:30, China +8, Bhutan +6, India (Arunachal Pradesh) +5:30, Myanmar +6:30.
...
you could define the able based on the rules #2 and #3...
and define regional areas between two longitudinal points... within a specified country.
I think the key to the breakdown based on a descending order of priority (+):
Default Time Zone based on Longitude
Continent
Country of Origin
Region of County
City / Other / Specific
And the big news... has anybody seen this government ftp site with all of the timezone data defined?
ftp://elsie.