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What is a Time Zone?

The term time zone can be used to describe several different things.

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A time zone is a region where the same standard time is used.

Time Difference from UTC

The local time within a time zone is defined by its offset (difference) from Coordinated Universal Time (UTC), the world's time standard.

This offset is expressed as either UTC- or UTC+ and the number of hours and minutes.

Time Zone Map – Always up-to-date

More Than 24 Time Zones

If each time zone were one hour apart, there would be 24 in the world.

However, the International Date Line, creates three more. In addtion, several time zones are only 30 and 45 minutes apart. This makes the total number of time zones worldwide much higher.

Not the Same as Local Time

The term time zone is often used instead of local time. For instance, during Daylight Saving Time (DST), it is common to say "California and Arizona are now in same time zone". However, the correct thing to say would be: "California and Arizona now have the same local time".

The reason is that California's local time during DST is UTC-7, but the standard time in California is minus one more hour: UTC-8. However, Arizona's local time is always UTC-7, because there's no DST in Arizona, and they remain on standard time all year.

Local Time Zone Names

Illustration image
Mountain Standard Time or Mountain Daylight Time or just Mountain Time?
The formal name for Mountain Time in the US is either Mountain Standard Time or Mountain Daylight Time.

To confuse matters more, each time zone has many different local time zone names, usually linked to the geographical name of the country or region.

The time zone names in the US are consistant: On the mainland, there are five time zones with five names and corresponding DST names. However, in other places in the world, the time zone names may be completely different, even though the UTC offset is the same.

For instance in Miami, Florida, the standard time zone is UTC-5, and it's called Eastern Standard Time – EST. In Havana, Cuba, the standard time zone is also UTC-5, but it's called Cuba Standard Time – CST.

Military Time Zones

There are also 25 military time zones which follow the 15 degrees longitudes. These are named according to the NATO phonetic alphabet: Alpha, Bravo, Charlie, etc. and are used in aviation, at sea and in telecommunications.

Identical Abbreviations

Another point that can cause confusion, is that some time zone's names in totally different places have exactly the same abbreviation. For example:

In many parts of the world, especially in countries with only one time zone, time zone names are not commonly used at all.

Time Zone Names and Codes Worldwide

Hot Political Potato

In most countries, the political decision to make adjustments regarding time zones or DST, is made for practical reasons, like saving energy, facilitating trade with neighbouring areas, or boost tourism.

In some cases, time zone borders and Daylight Saving Time are used as a a political tool, most recently in Russia, Ukraine, and North Korea.

When and Why?

The expansion of the railway, and other transport and communications, as well as trade globalization, during the 19th century created a need for a more unified time-keeping system, and time zones were introduced.

Topics: Time Zone, Timekeeping

Coordinated Universal Time (UTC)


Wednesday, October 26, 2016

UTC is the common time standard across the world

More about UTC


Time Zones Worldwide

Time Zone Map With DST

Time Zone Map

Time Zone Library

  1. What is a Time Zone?
  2. How Many Time Zones Are There?
  3. Half Hour & 45 Minute Time Zones
  4. What is Standard Time?
  5. What's the International Date Line?
  6. When Were Time Zones Introduced?
  7. USA Time Zones
  8. UK's Time Zones: GMT and BST
  9. Canada's Time Zones
  10. Australia’s Time Zones
  11. Antarctica's Time Zones

Time Zones Worldwide

Time Zone Tools

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