GMT +8 (UTC+8) Countries 2025

GMT+8 countries are countries which lie partially or completely within the GMT+08:00 time zone, where the local time is eight hours ahead of Greenwich Mean Time (GMT+00:00), which is the time in Greenwich, England. GMT has actually been replaced by Coordinated Universal Time (UTC), although GMT remains the more commonly known of the two terms. As such, the GMT+8:00 time zone is also known (more correctly) as UTC+08:00. GMT+8 also has several region-specific alternate names, including China Taiwan Time (CCT), Western Standard Time (Australia), Hong Kong Time, Irkutsk Time, and more. Located in Eastern Asia, UTC+08:00 is one of the earliest time zones in the world (UTC+12:00 being the earliest).

GMT+08:00/UTC+08:00 has a larger population than any other time zone in the world, and is home to an estimated 24% of the Earth’s inhabitants. This is primarily due to an unusual decision by the government of China, one of the two most populous countries in the world (along with India). Although China’s geographical area stretches across five time zones, the country’s government has chosen to use only GMT+8:00 across its entire expanse. Thus, China’s full population falls into UTC+08:00.

Countries in the GMT+08:00/UTC+08:00 Time Zone

The Importance of Greenwich Mean Time (GMT)

Originally developed by British railroads in the 1840s and made a global standard at Washington DC’s International Meridian Conference in 1884, Greenwich Mean Time established a universal international standard time system that enabled the coordination of time all around the world. GMT divides the world into 26 time zones—one for each hour in the day plus two overlapping extras to accommodate the remote Pacific Island country Kiribati—each running vertically from Earth’s north pole to its south pole. Time zones are named according to their distance from the longitudinal meridian that passes through Greenwich, England and establishes the GMT+0:00 time zone.

While the borders between time zones are clearly defined, they are also notably flexible. Countries whose territory touches more than one time zone are free to choose which of those time zones they wish to utilize. For example, the countries of Turkmenistan, Iran, and Oman are geographically positioned in a vertical north-south row, but they adhere to three different time zones (including Iran’s custom GMT+03.50).

Greenwich Mean Time (GMT) compared to Coordinated Universal Time (UTC)

The term GMT is often used incorrectly, especially among English speakers, as it technically refers only to the time zone in which Greenwich, England is located (GMT+00:00). The more correct label for time zones is Coordinated Universal Time, or UTC.

When time zones were first introduced, the time was calculated and timekeeping devices were calibrated by measuring the movement of astronomical bodies—particularly the rotation of the Earth. However, as technology progressed, scientists realized that the speed of Earth’s rotation is not constant, but fluctuates by fractions of a second at both predictable and unpredictable intervals. While a discrepancy of a few seconds a day made little difference 100 years ago, in the modern era even such a small variation can have a negative impact on sensitive scientific and technical operations.

To alleviate this concern, time is now calculated using atomic clocks such as hydrogen masers and cutting-edge “cesium/caesium fountain” clocks, which will not gain or lose a second of time in 100 million years. Atomic clocks are operated in groups—for instance, the US National Institute of Standards and Technology operates twenty atomic clocks in Boulder, Colorado—in climate-controlled areas and their times are compared to ensure accuracy.