There is no unified national standard time in the United States. In order to avoid confusion, media and news organizations usually clearly indicate the time zone and time when reporting. Beijing and Washington are located in the East Eighth District and the West Fifth District respectively. Under normal circumstances, the time difference between the two places is 13 hours, or 12 hours in case of daylight saving time.

According to the division standard of world time zones, the United States spans six time zones, from the fifth west zone to the tenth west zone. Each time zone corresponds to a standard time, which is Eastern Time (EST), Central Time (CST), Mountain Time (MST), Pacific Time (PST), Alaska Time (AKST) and Hawaii Time (HST) respectively from east to west, and each time is reduced by one hour according to the law of "East Early and West Late". The so-called western time refers to Pacific time.

The time zone boundaries in the United States are not completely divided according to the meridian, and basically take care of the natural boundaries of each state. Different time zones cover different cities and states of different sizes. For example, PST includes four States along the Pacific coast, including cities such as Los Angeles, while EST includes 19 States along the Atlantic coast, near the mainland and Washington, D.C., with Washington as the representative city.

The representative city of MST is Salt Lake City, Utah, and the cities that implement CST are Chicago and New Orleans. AKST and HST are limited to Alaska and Hawaii.

Note: The standard time for China to implement national reunification is Beijing time.