The world UT

GMT: also known as universal time. Greenwich mean time. It's not just astronomers who use Greenwich mean time, it's a term that's often used in the news. We know that every place has local time. It would be complicated and inconvenient to record a major international event in local time. And it's easy to get things wrong in the future. So astronomers came up with an acceptable and convenient way to record it, which was to use Greenwich mean time. Greenwich is the home of the former Greenwich observatory on the southern outskirts of London, England, which is also the starting point of the geographical longitude in the world. Major events in the world are recorded in Greenwich time. Once Greenwich time is known, one can easily work out the local equivalent. For example, if something happens at 8am GMT, China is east of the UK, and Beijing time is 8 hours earlier than GMT, we immediately know that it happened at the same time as 16:00 Beijing time, which is 4pm Beijing time, which is from east +8 time zones +8 hours.