About Time and Time Zones

The Earth rotates from west to east, so the east sees sunrise earlier, and the time in the east is earlier than the time in the west. The time difference between east and west is not only calculated in hours but also involves minutes and seconds. This complexity has caused inconvenience for the global use of time.

To simplify the use of time and resolve time confusion, the International Meridian Conference held in Washington in 1884 established a globally unified standard for time zones. The Earth is divided into 24 time zones, including the Central Time Zone (zero time zone), East 1-12 zones, and West 1-12 zones. Each time zone spans 15 degrees of longitude, with a time difference of exactly 1 hour. The East and West 12th zones uniquely span 7.5 degrees of longitude, bounded by 180 degrees east and west longitude. The time adopted by the central meridian of each time zone is known as the zone time, serving as the unified time within that time zone. For instance, China uses East 8th zone time (Beijing Time), which is 1 hour faster than Thailand's time in the East 7th zone, and 1 hour slower than Japan's time in the East 9th zone.

Adjusting the time is crucial when traveling across time zones. When moving west, for every time zone crossed, you need to set your time back by 1 hour. When moving east, you need to advance your time by 1 hour.

In reality, many countries and regions do not strictly follow time zone divisions to calculate time. Instead, they adopt a unified time based on their actual needs. For example, China uses East 8th zone time throughout the country, which is the time of the time zone where Beijing is located, referred to as Beijing Time. European countries such as the UK, France, the Netherlands, and Belgium, have adopted East 1st zone time in order to align with most European countries, despite being geographically located in the Central Time Zone.

Note: The implementation of Daylight Saving Time (DST) usually advances time by 1 hour compared to standard time. For example, during DST, 10 AM in standard time becomes 11 AM in DST. The implementation times of DST vary across countries, and adjustments need to be made according to local policies when traveling.