1, also known as universal time. Greenwich mean time. Now, not only astronomers use Greenwich Mean Time, but also the term often appears in newspapers and periodicals. We know that every place has its own time. It will be complicated and inconvenient to record major international events in local time, and it will be easy to make mistakes in the future. Therefore, astronomers put forward an acceptable and convenient recording method, which is based on Greenwich local time. Greenwich is the location of the former Greenwich Observatory in the southern suburbs of London, England, and the starting point of the world geographical longitude. Major events in the world are recorded in Greenwich local time. Once Greenwich Mean Time is known, it is easy to calculate the local time. For example, an event happened at 9: 00am GMT, China was in the east of England, and Beijing time was 8 hours earlier than GMT, so we immediately knew that the event happened on the same day 17 GMT.

2. Eastern Time refers to the local time in the eastern United States. The United States spans six time zones from the West Fifth District to the West Tenth District. Each time zone corresponds to Eastern Standard Time from east to west, namely Eastern Time (est) (West Zone 5 Time), Central Time (CST) (West Zone 6 Time), Mountain Time (MST) (West Zone 7 Time), Pacific Time (west eight Zone Time) (PST) and Alaska Time (AKST) (West Zone 9 Time). Greenwich mean time, also known as Greenwich mean time, is local time. Refers to the standard time of the Royal Greenwich Observatory in the suburb of London, because the prime meridian is defined as the meridian passing through it. Starting from February 5th 1924, Greenwich Observatory will release time adjustment information to the world every hour.