Don Pedro's Timezone Explanation

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Time Zones are Important

As the sun moves from East to West, so time proceeds the same way. Our planet Earth turns a full circle (360°) in 24 hours. 360 divided by 24 gives 15°. That is why 15° longitude equals 1 hour in time difference.

When the business hours start in the yellow area in the map below, then the business hours will just finish in the blue area to the right (East). When the business hours start in the blue area to the left (West) they will just finish in the yellow area.

To achieve a faster download for your visitors you choose a server at a location in the blue area while your visitors are in the yellow one. Then most people will come to your site when the server is not busy. Your pages will download fast.

West<-- WORLD MAP -->East

50°

(2)

120°

(1)

42°

120°

(3)

28°

(4)

The vertical lines are longitudes. The degrees (i.e. 50°) gives the width of each area in longitude degrees.

During 2006 Broadband has penetrated USA almost completely, to a great extent also North Western Europe, some places in the Middle East, especially so in Singapore, Hong Kong, and Japan. This doesn't, however, mean you can disregard the download time variations. There are two reasons for this.

It's being said people on average wait 7-8 seconds before they move to the next website. This is still valid for slow connections (modem and telephone line), which is what the majority of the world is using. The other reason is; when a person changes over to Broadband connection, he/she very fast gets accustomed to the new greater speed. Now that person wont wait anymore so long, may be 4-5 seconds only.

You can do this yourself.

Take a small size World map and cover it with a transparent plastic sheet. Fasten the plastic sheet with thumbtacks or something like that so it doesn't move over the map. Then you follow the steps below:

Mark the Western limit of your target area (line 1).
Mark the Eastern limit for the location of your server at 120° (8 hrs x 15°) West of line (1). This gives you line (2). When the time is 05 PM (1700 hrs) at line (1) it is 8 hrs less = 09 AM at line (2).
Mark the Eastern limit of your target area = line (3).
Mark the Western limit for the location of your server at 120° (8 hrs x 15°) East of line (3) This gives you line(4). When the time is 09 AM at line (3) it is 8 hrs more = 05 PM (1700 hrs) at line (4).

If you leave 30° longitude for your target area it will leave you 90° of longitude (6 time zones) for your server location area. The wider your target area, the less is left for your server location area (and vice versa). The optimal location for your server is at the middle longitude of your server location area (blue area).

This means, when you have business hours in the yellow area, it's always outside business hours in the blue one.

Example.

If you chose as your target area (yellow area) Europe, then the Western limit of your target area (1) would be about at Glasgow/Birmingham (UK) = 008°W. This would give 008° + 120° = 128°W, which is just West of Vancouver (W. Canada) or just East of Hawaii/Alaska as the Eastern limit of your server location (blue) area (line 2).

The Eastern limit for your target area (yellow) could be just East of Cyprus = 034°E (3). This gives 034° + 120° = 154°E, which is just East of New Guinea/Australia as the Western limit of your server location (blue) area (line 4). Unfortunately the optimal location for your server would in this case fall in the middle of the Pacific!

Your server location for Europe as a target, could then be either Hawaii/Vancouver/California or East Australia/Japan/New Zealand.

If you, on the contrary, want to target Asia, then you should choose as optimal server location E. Canada/US = Quebec/Montreal/New York.

How to Calculate time zones

The time zones are an approximation of different times when the sun "passes" the place where you live. Of course it's not the sun that moves, it's the earth that rotates. Each rotation takes 24 hours. Or let's say the time it takes for the earth to make one full rotation has been divided into 24 hours.

Several hundred years ago there was a well known astronomic study centre ( observatory ) at Greenwich in UK. The longitude that passes through Greenwich was therefore taken as the "zero" longitude. The "time" in Greenwich zone is called "Greenwich Mean Time". Because the French want to be different from the British, they use something called "Universal Co-ordinated Time" ( UTC ), which is same as Greenwich Mean Time, only different name.

A longitude is a line drawn from the North Pole to the South Pole. Because this line is perpendicular to the Equator the time is always the same everywhere on the same longitude. North or South of the equator makes no difference.

Because a circle is defined to have 360 degrees of arc you divide this by 24 and get 15 degrees of arc per hour - 15 x 24 = 360. Each time "zone" is therefore 15 degrees wide.

To make "time zones" you place the first, the "zero" zone on the Greenwich longitude, so you have 7.5 degrees on the West side and 7.5 degrees on the East side, which means the "zero" longitude passes straight along the middle of that time zone. Then the first time zone to the East stretches from 7.5 East to 22.5 East and so on. Same towards the west.

To calculate what time in another place from where you start the calculations it's easiest to always go via Greenwich.

Example: Say I'm living in the Philippines, it's 11.00 in the morning local Philippine time. Philippines is 8 hours ahead of Greenwich, because it's to the East (GMT + 08). So 11.00 minus 8 is 03.00 in the morning (Wednesday) at Greenwich. If you now wanted to know what time it is in California, USA, at 09.00 in the Philippines, then you continue towards West.

To make it still easier you use the 24 hour system, so when you again deduct 7 hours from 03.00 you first add 24 hours to the 3 hours. Means 03.00 on the morning of this Wednesday equals 27.00 on Tuesday, then 27 - 7 = 20.00 on Tuesday, which is 8 on Tuesday evening in California. The "7" in time difference comes from New York being 4 hours behind Greenwich and California being 3 hours behind New York (still further West) - 4+3=7.

Or, 11.00 in the morning in the Philippines gives a time 15 hours less (to the West - via Greenwich), i.e. 8 + 7 = 15, than California. So 24 + 11 = 35 - 15 = 20 hrs the day before.

Usually the actual time zone for a specific country is taken as the one closest to the country's capital. With exceptions for some countries which stretches very far in the East-West direction, like USA, Russia, China, and Indonesia. These all cover several timezones. The only country that have a timezone which isn't a full hour is, as far as I remember, India. India is GMT + 4.5 (?) hours, ahead of Greenwich.

If you calculate time zones involving "daylight saving time", remember that is something temporary only. Daylight saving time doesn't change the time zone. There's only a change of one hour (North America and Northern Europe) temporarily for a certain time period (March - September). It changes ONLY the time the watches show during that time period. In such a case you simply use "winter time" in your calculations instead.

You can also get a world map with time zones. Note: North Europe is using "Summer Time", i.e. Local time + 1 hour from end of March to end of October.

Time Zone Explanation

Time Zones are Important

You can do this yourself.

Example.

How to Calculate time zones