Timezone calculator.

[anarky]

Boy, do we have a can of worms regarding timezones.

I consulted my Encyclopaedia Britannica and World Book Encyclopedia and they both define 24 standard timezones.

There are numerous exceptions, but for this challenge, we will use the 24 timezones on the following list. I have included principal country/city names.

Also for this challenge, we will ignore the issue of daylight savings or summer time. It becomes almost impossible for our program to determine if the subject timezome uses daylight savings, when it starts and ends, and whether it advances one hour or two. Therefore, we will leave this daylight time adjustment up to the user of the program.

TIMEZONES:
GMT = London
GMT - 1 = Reykjavik
GMT - 2 = Greenland
GMT - 3 = Rio de Janeiro, Brazil
GMT - 4 = Santiago de Chile
GMT - 5 = New York
GMT - 6 = Chicago
GMT - 7 = Denver
GMT - 8 = Seattle
GMT - 9 = Alaska
GMT -10 = Honolulu
GMT -11 = Midway Island
GMT -12 (does not exist, see GMT +12)

continuing in a circle around the world............
GMT +12 = New Zealand
GMT +11 = Solomon Islands
GMT +10 = Sydney
GMT + 9 = Tokyo
GMT + 8 = Hong Kong, and China
GMT + 7 = Bangkok
GMT + 6 = Omsk, Russia
GMT + 5 = Karachi
GMT + 4 = Stalingrad
GMT + 3 = Moscow
GMT + 2 = Cairo
GMT + 1 = Berlin

Comments?
*****

It's easy to add the non-standard timezones. DST is harder, since that splits Australia up into a real mess. Darwin is GMT +9:30. So is Adelaide. Darwin and the NT do not have DST. Adelaide and SA do. Brisbane in QLD does not have DST, NSW, Vic and Tas have DST. WA does not. For ease of reading, I won't include the ACT, which is surrounded by NSW anyway.

During the winter time of the year, such as now, we have:

GMT +8:00 WA
GMT +9:30 SA, NT
GMT +10:00 QLD, NSW, ACT, VIC, TAS

During summer months:
GMT +8:00 WA
GMT +9:30 NT
GMT +10:00 QLD
GMT +10:30 SA
GMT +11:00 NSW, ACT, VIC TAS

Then what about the middle east? Last I heard, the whole area is one time zone, instead of 5 or 6.

The former USSR? 11 zones...

My opinion would be the following: include the GMT +/- x:30 non standard timezones. Don't include DST.

BTW, I live in SA. That makes me GMT +9:30 atm.

EDIT: According to http://wwp.greenwichmeantime.com/info/timezone.htm, Kiribati islands is over a day behind New Zealand. So Thursday in NZ is still Tuesday in Kiribati Is.

>anarky