World City Clock Time Zone Listing

What are World City Time Zones?

Shows the world time and date for cities in all time zones.

A time zone represents an offset applied to Greenwich Mean Time (GMT) to obtain local time. The offset might vary throughout the year, if daylight savings time (DST) is used, or might be the same all year long. Typically, regions closer to the equator do not use DST. If DST is in use, then specific rules define the point at which the offset changes and the amount by which it changes.

A time zone is a region of the globe that observes a uniform standard time for legal, commercial and social purposes. Time zones tend to follow the boundaries of countries and their subdivisions instead of strictly following longitude because it is convenient for areas in close commercial or other communication to keep the same time.

Why are there 24 time zones?

A time zone is a designated area where the same standard time is followed. The planet is divided into time zones longitudinally, with each zone approximately 15 degrees apart, representing a one-hour time difference. Some countries have half-hour time zones, making the total number of time zones more than 24. The starting point of the Synchronized Universal Time (UTC) is the Prime Meridian (zero longitude). The International Date Line (IDL) is located at 180 degrees longitude and marks the change of days. As you travel west of the IDL, time moves forward incrementally.

The Earth's rotation and time create 24 time zones.

The concept of dividing the world into 24 time zones is closely linked to the Earth’s rotation and the idea of time itself. Here’s how it works:

1. Earth’s Rotation: The Earth rotates 360 degrees in about 24 hours. This rotation happens at a pretty steady rate. This means the Earth rotates about 15 degrees each hour (since 360 degrees/24 hours = 15 degrees per hour).

2.A Global Standard: Before the late 19th century, every city or town set its own local time based on the sun's position. This made coordinating activities across different places very difficult, especially with the advent of fast long-distance travel like railroads and telecommunication technologies. This led to the establishment of a global standard for timekeeping. 

3. Standard Time Zones: The International Meridian Conference in 1884 decided to divide the world into 24 standard time zones. Each time zone spans 15 degrees of longitude, reflecting the Earth’s rotation rate. This makes it easier to know the time in another part of the world and coordinate activities across different locations.

4.Prime Meridian: The starting point for these time zones is the Prime Meridian, defined as 0 degrees longitude and runs through the Royal Observatory in Greenwich, London, UK. This line, also known as Greenwich Mean Time (GMT), serves as a reference point for all other time zones. Time zones to the east of the Prime Meridian are ahead of GMT, while those to the west are behind GMT.

Notably, actual time zone boundaries are not strictly along the 15-degree segments due to political and geographical considerations. Also, only some places observe the 1-hour increments. Some places have their standard time set to a half-hour or even a quarter-hour different from the standard times.

Regions with a quarter of an hour timezones offset

There are a few regions in the world that use time zones offset by a quarter of an hour. Here are some examples:

1. Nepal: Nepal Standard Time is UTC+5:45, a 45-minute increment from the standard time zone. Nepal uses this time zone because it aligns closely with the mean solar time at Kathmandu, the nation's capital.

2. Chatham Islands, New Zealand: Chatham Standard Time is UTC+12:45, and Chatham Daylight Time is UTC+13:45. The Chatham Islands, about 680 kilometers southeast of mainland New Zealand, use these unusual time zones due to their unique geographical position.

3. Central Western Time zone of Australia: A small region in Western Australia, including the town of Eucla, unofficially uses a time zone known as Central Western Time, which is UTC+8:45. This time zone is not officially recognized by the Australian government but is used in practice due to local geographical considerations.

It’s important to note that while these time zones are unusual, they work well for the regions that use them due to their unique geographical or political circumstances.