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Understanding Time Zones

Tuesday, September 3, 2013 by — creator of Time Genie

Updated: Friday, March 11, 2016

Time Genie provides you with the current time in more than 65,000 hand–picked cities or locations around the world in 42 time zones. But how is a time zone chosen? Who chooses the time zone? Why or what factors are used to determine the time zone for a city, location or country?

To learn the answers to these questions and more, keep reading (or watching).


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Time Zones — Video

NASA Kid Science News helps explains time zones in this video

Time Zones Explained

Not everyone understands exactly how time or time zones are determined. There are a few factors that determine the time or time zone that a country or city is located in.

Sunrise and Sunset

Let's start with the most basic aspects when considering what time zone a location should or could be in — sunrise and sunet.

Many people will tell you that a time zone is determined based on the longitudal co-ordinates and yes, this is true for many locations. But throw away this scientific approach for a moment and just think with a common sense point of view, that is, when does the sun rise and when does the sun set?

When you think in terms of sunrise and sunet then you will begin to see that you wouldn't want sunrise to happen at 1 AM or even 9 AM. You would want sunrise to happen somewhere around or between to 5 to 7 AM.

Realizing this, a city, state, province or country can then set or change their time zone so that sunrise happens at a reasonable time. In turn, this ensures the daylight hours are maximized.

When the sun rises and when the sun sets is major factor in choosing the time zone especially for countries that are close to or along the equator. Why? Because throughout the whole year, the amount of daylight for locations near the equator may fluctuate no more than 1 hour. This is opposite to a country that is located further north or south where there is less daylight in the winter and more in the summer.

Along or close to the equator, sunrise and sunet occur at approximately the same time throughout the whole year. Considering this, a country close to the equator will determine its time zone based on when the sun rises and when the sun sets. A country in this sort of location will generally speaking choose a time zone whereby their sunrise is somewhere between 5 to 7 AM and sunset will then happen around 6 to 8 PM. A country would not make their sunrise at 8 AM and sunset at 9 PM — but if they really wanted to, they could.

Determining the time zone, when thinking in terms of sunrise and sunet, is a basic and simple way of understanding how a country or a location determines its time zone.

A lot of countries in Africa, Asia, the Caribbean, Central America, Indian Ocean, the Middle East, Oceania and South America are examples of where the time zone is determined by sunrise and sunet.

But there are other factors to consider also...

Financial, Economic and Logistical Reasons

A country or location may choose to be in certain time zone for financial, economic and/or logistical reasons.

A country like Malaysia spans a huge distance. In theory, Malaysia could have two time zones. However, the government of Malaysia thought it was best to keep the whole country in the same time zone. Thus, a town like Kudat, which is located in the eastern part of Malaysia may have sunrise around 6:30 AM whereas a city like Kuala Lumpur, located in the western part of the country will have sunrise around 7:30 AM.

Why do these two cities that are in the same time zone have different sunrise and sunet times?

Well, it all has to do with one very basic fact which is that the sun rises in the east and sets in the west. As a result, a town in the eastern part of a country will see the sun rise before the western part of the country. If there is a large enough distance between the eastern and western part of the country, then it will take the sun time to travel from the eastern part of the country to the western part of the country.

A country like Singapore, which is located at the bottom of Peninsular Malaysia uses the same time as Malaysia even though Singaporeans may prefer to have sunrise at 6:30 AM rather than 7:30 AM. But since Singapore is financially, economically and logistically tied to Malaysia, Singapore uses the same time as Malaysia to keep things running smoothly.

Jurisdictions

Who legally determines what time zone a location is in?

The answer is that it all depends on the laws of the country.

A country like China, which is really wide, should in theory have at least 3 time zones but the government of China has chosen to have the whole country in the same time zone similar to Malaysia.

If you compare the sunrise and sunet times for Shanghai, which is located in the eastern part of China, to the sunrise and sunet times in Lhasa (Tibet), located in the western part of China, then you will see there is a huge difference. Sunrise in Shanghai might be at 6:30 AM while sunrise in Lhasa will be probably closer to 9 AM. Meanwhile, sunset in Shanghai will be around 5:30 PM and sunset in Lhasa will be at around 7:30 PM. Yet, both cities share the same time as do all cities within China.

So first and foremost, a country can determine its own time zone. A country like Nepal has chosen to be in an interesting time zone which is GMT +5:45. Why would Nepal choose such a crazy time zone? The reason is simple... to maximize the most daylight for each day. Sunrise in Nepal may occur around 6:45 AM and then set around 6 PM. Basically Nepal is squeezing as much sunlight as it can out of each day (see the time in Kathmandu page or the sunrise and sunset times for Kathmandu).

In addition to a country determining its time zone, a state or province of the country can also determine the time zone. Russia is the ultimate country for time zones because the country is so wide that it has to be separated into numerous time zones. Countries like Canada, the USA, Australia, Brazil and Indonesia are examples of other countries that have multiple time zones— but there are more countries with multiple time zonesincluding Kiribati. In some of these countries, a state or province has influence over the time zone used.

But wait, there's more! Oh yes, there's more...

Time itself can be pinpointed not only by country, by state or province, but also by the city. In some locations, the time is determined by the city. Realizing that in many situations it is the city that determines its time zone, Time Genie is specifically organized and able to pinpoint the exact time for each city. In turn, this makes Time Genie your best source for time and date information!

Longitude

Each 15 degrees of longitude is considered a new 1 hour time zone. Since there are 360 degrees of longitude, this means there are 24 time zones— in theory this is correct, but in reality it is not. At Time Genie, we feature 42 time zones.

Many locations choose to use a non–standard time zone offset. As a result, there are more than 24 time zones in the world. Examples of non–standard time zone offsets include:

GMT -9:30GMT -3:30GMT -2:30GMT +3:30GMT +4:30GMT +5:30GMT +5:45GMT +6:30GMT +8:45GMT +9:30GMT +10:30GMT +11:30GMT +12:45 — and GMT +13:45.

Although technically a standard time zone offset because they are on the hour, GMT +13:00 and GMT +14:00 are unusual because they are greater than 12. That is, if you go by the theory there are 24 time zones, then it means that the time zones can only go from GMT -12:00 to GMT +12:00.

Since there are more than 24 time zones, we can begin to see that the rule that every 15 degrees of longitude equals a new time zone is not a rule, but a guide. Many times are influences by this view.

This rule that every 15 degrees of longitude equals a new time zone that is increased or decreased by 1 hour is used more prevalently by ships. This is known as nautical time.

A map of the world showing the lines of latitude and longitude
A map of the world showing the lines of latitude and longitude — map copyright Time Genie.

Time is Arbitrary

Ultimately, what time zone is used is a choice determined not by a rule that must be followed, but by what works best for the country, state, province, city, location, etc.

Organized By City

What makes Time Genie such a valuable web site is that Time Genie features the time based on the individual location, not just the country, state or province.

Time itself must be determined, at the most fundamental level, by the city or location. As a result, Time Genie is ultimately organized by city and not by country, state or province.

The benefit to you, when using Time Genie, is that in addition to finding the current time by country, by state, by province and by region, you can also find the current time by city.

Interesting Time Zones

Antarctica

Antarctica makes an interesting place for time.

In Antarctica, the time zone is determined by the country that operates the research station.

Most research stations do not use the same time zone as their home country, but rather the same time zone as the country from which they make their trip to Antarctica from. So for example, the USA research stations such as Amundsen–Scott South Pole Station tend to have the same time as New Zealand since the USA scientists all leave for Antarctica from Christchurch, New Zealand. Other research stations will have the same time as Chile, Argentina or possibly South Africa if they depart for Antarctica from one of these locations. This is done to help co–ordinate shipments of supplies, etc in a more efficient way as everyone is then using the same time.

While some research stations use the same time zone as their home country, Troll Station does a bit of both — that is, part of the year Troll Station is in the GMT time zone to better co–ordinate with locations from which they get supplies and then during the Antarctic winter, Troll Station changes between GMT +1 and GMT +2 to be in the same time zone as Norway. In fact, Troll Station is the only location in the world that uses 3 different time zones.

→ Learn more about time zones in Antarctica.

→ Learn more about Troll Research Station.

Map of Antarctica
Map of Antarctica — map copyright Time Genie.

Australia

For the most part, Australian time zones help maximize daylight hours. But within Western Australia, there is a problem.

Officially, all of Western Australia is GMT +8. This is a good time zone for most cities and towns in Western Australia which are located are near the coast — the Indian Ocean to be exact. But there are a few remote locations in Western Australia where GMT +8 doesn't make sense. Thus, these towns have adopted an unofficial time zone of GMT +8:45. But there is also a weather reporting station that uses the same time zone as South Australia.

Border Village, Caiguna, Eucla, Madura and Mundrabilla are all unofficially GMT +8:45.

Giles Weather Station, also referred to as simply Giles, is located near the border with South Australia. Giles is a manned weather station but due to its close proximity to South Australia combined with its longitudal co–ordinates, it only makes sense that Giles be in the GMT +9:30 time zone — which is the same as South Australia.

Lord Howe Island is another interesting time zone within Australia. When it comes time to switching from standard time to summer time, instead of changing 1 hour, Lord Howe Island only changes 30 minutes between GMT +10:30 and GMT +11. This is due to the fact that Lord Howe Island is situated off the coast of New South Wales in the Tasman Sea. It's far enough away from the mainland to require a slightly different time, but not so far that it needs to switch by 1 full hour either.

Map of Australia
Map of Australia — map copyright Time Genie.

French Southern and Antarctic Territories

Quite possibly you've never heard of the French Southern and Antarctic Territories, but it exists. Officially it is known as Territoire des Terres australes et antarctiques françaises, or simply TAAF for short.

The French Southern and Antarctic Territories spans from islands in the Indian Ocean between Africa and Madagascar known as the Scattered Islands all the way to islands halfway between Africa and Australia.

Although only 4 time zones are used in the French Southern and Antarctic Territories which are GMT +10, GMT +5, GMT +4 and GMT +3; the actual territory spans 7 time zones.

Map of French Southern and Antarctic Territories
Map of French Southern and Antarctic Territories. Notice how the islands go fro approximately 40° E to 90° E — map copyright Time Genie.

Hawaii

When you think of Hawaii, you probably think of Honolulu. But in reality, the Kingdom of Hawaii covers a huge distance. As a result, the French Frigate Shoals along with Tern Island and Kure Atoll all have a 1 hour time difference compared to the major islands in Hawaii. Never heard of these islands before? You are not alone. These islands are more remote and are definitely not tourist destinations. Although we hear the mai tais available on Tern Island are cheap!

Map of Oceania
Map of Oceania showing Hawaii in the top right corner — map copyright Time Genie.

Hispinola Island

Located on Hispinola Island are the two countries of Haiti and Dominican Republic. Although located on the same island, these two countries use different time zones except when and if Haiti observes daylight saving time. If Haiti observes daylight saving time, the both Haiti and the Dominican Republic are in the same time zone for half of the year. Otherwise, there is a 1 hour time difference between these 2 countries.

Map of Hispinola Island (Haiti and Dominican Republic)
Map of Hispinola Island showing Haiti on the left and the Dominican Republic on the right — map copyright Time Genie.

Iran

There's not a lot that is special about the time in Iran, although Iran does use a non–standard time zone offset that is GMT +3:30 during the winter and GMT +4:30 during the summer. A non–standard time zone offset means that instead of being on the hour they are on the half hour or another number. But what's most interesting about Iran is that when the country changes to summer time, the day on which the change is made is not based on the Gregorian calendar like western countries, but based upon the Persian calendar which is solar based. The Persian calendar is also known as the Solar Hijri Calendar.

For Persian speakers and users, Time Genie actually shows the date on some pages both based on the Gregorian calendar and the Solar Hijri calendar. Users can view the Persian / Farsi version of Time Genie at fas.timegenie.com

Map of Iran
Map of Iran — map copyright Time Genie.

Kingdom of Elleore

The Kingdom of Elleore is technically a micronation. The Kingdom of Elleore is a silly place where children are meant to have fun. There are many unusual traditions at the Kingdom of Elleore — one of which is that the time zone should be GMT +0:48 during the winter and GMT +1:48 during the summer.

Although a micronation, the Kingdom of Elleore is essentially located within Denmark.

Map of Denmark
Map of Denmark — map copyright Time Genie.

Kiribati

Kiribati is probably one of the most confusing locations in the world when it comes to time zones. But Kiribati's time zone is not the only thing that is confusing about Kiribati — so is its name.

In the Gilbertese language, a ti combination is actually pronounced as an s. Thus, Kiribati actually sounds like Kiribas. The name Kiribati is the local pronunciation for Gilberts. The Gilbert Islands chain are the main island chain in the country and named after Thomas Gilbert who was the first European to discover these islands.

It's worth noting that the islands known as Kiritimati is also known as Christmas Island. Similar to Kiribati, the name Kiritimati is the local Gilbertese spelling for Christmas. When you change the ti become an s then Kiritimati changes to Kirismas — or — KIRR-is-mas.

When it comes to time zones in Kiribati, it's first important to remember that Kiribati is a group 33 coral atolls in the South Pacific Ocean. The islands are divided into 3 island groups known as the Gilbert Islands, the Phoenix Islands and the Line Islands. Kiribati is basically along the equator but Kiribati also straddles the International Date Line. This is where, for many, it starts to get confusing.

The International Date Line is an imaginary line that basically says, as an example, when it is Wednesday on one side of the line it will be Thursday on the other side. Since Kiribati is on both sides of the International Date Line, in theory, one part of Kiribati could be on Wednesday while the other part could be on Thursday! Can you imagine how confusing this might get as you are watching television and see an advertisement for an upcoming show...

Don't miss the next episode of the Survivor Kiribati at 9 PM on Thursday on Tarawa Atoll and the Gilbert Islands, 8 PM on Thursday on Rawaki Island and the Phoenix Islands and finally, at 7 PM on Wednesday on Christmas Island and the Line Islands!

To solve this problem of having one part of Kiribati be on one day and the other part on another day, the government of Kiribati has decided to ignore the International Date Line and keep the whole country on the same day, albeit in 3 different time zones which are GMT +12, GMT +13 and GMT +14.

Just to make things a little more confusing for you, Christmas Island, which is located in the most eastern part of Kiribati is in the same time zone as Hawaii, yet, when it is Thursday on Christmas Island, it is still Wednesday in Honolulu even though they are in the same time zone and even though Christmas Island is basically directly south of Honolulu!

Map of Kiribati
Map of Kiribati. Notice how the islands are on either side of the 180° longitude — which is the International date line — map copyright Time Genie.

Märket Island

Märket Fyr (Market Reef) is an island, approximately 300 meters long and about 80 meters wide. To put this into perspective, the current world record for running 400 meters is less than 50 seconds. So in theory, the world's fastest man could run across this island in less than 1 minute.

The only problem is that Märket Fyr, which is situated in the Baltic Sea, belongs to two countries. This small island is divided in half whereby one side belongs to Sweden and the other side belongs to the Åland Islands which is an autonomous region of Finland. So while the world's fastest man could in theory run across this island in less than 1 minute, he would be delayed when showing his passport at the immigration office!

What really makes Märket Fyr really interesting is that Sweden and Åland Islands (Finland) are located in different time zones. Thus, this small island also has two time zones. One half observes the same time as Sweden and the other half observes the same time as Finland!

Map of Åland Islands
Map of showing Åland Island, Sweden and Finland. Märket Fyr is located between the Åland Island and Sweden — map copyright Time Genie.

Nepal

Nepal has chosen, in order to maximize its daylight each day, to use a non–standard time zone offset and so unlike some countries which are on the half hour, rather than the hour, Nepal is on the 45 — GMT +5:45 to be exact.

Map of Nepal
Map of showing Nepal — map copyright Time Genie.

New Zealand

Similar to Nepal, Chatham Island which is part of New Zealand, is on the 45 also — GMT +12:45 during the winter and GMT +13:45 during the summer!

Map of New Zealand
Map of New Zealand. The Chatham Island are the small islands located to the right of the North Island and South Island — map copyright Time Genie.

Samoa

The distance from Western Samoa to American Samoa is really nothing more than a hop, skip and a jump — plus a bit of a swim. But although the two countries are really close in terms of distance and of course, in terms of culture, they are world's apart in terms of a time zone. In the past, both Western Samoa (now referred to as Samoa) and American Samoa were in the same time zone. But Western Samoa decided to change their time zone to be more in harmony with Australia and New Zealand. So Western Samoa is the GMT +13 time zone while American Samoa is in the GMT -11 time zone — this is a 24 hour time difference and so the actual time is the same, but when it is 12:30 PM on Wednesday in Western Samoa, it is 12:30 PM on Tuesday in American Samoa.

To make things a little bit more confusing, Samoa also observes daylight saving time. As a result, during daylight saving time, not only are Samoa and American Samoa 1 day apart, but now they are 1 day plus 1 hour apart.

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