Time in different cities is determined by their belonging to time zones, or zones. Having opened the corresponding map in front of you, you can find out the time anywhere in the world.
Due to the rotation of our planet around the Sun at one point on the Earth it can be day, and at another - night. Therefore, for the convenience of residents and for calculating the time, the planet was conditionally divided into time zones, or zones. There are 24 of them in total, as well as hours in a day. The belts stretch from one pole of the Earth to the other in accordance with the meridians. Therefore, the prime meridian simultaneously limits the zero time zone, which is measured from the Greenwich Observatory near London.
East of Greenwich, in each time zone, counting in order, one hour is added. Accordingly, to the west, time, on the contrary, also decreases by 1 hour. Therefore, if, when determining time zones, they write "Moscow, +3: 00", this means that our capital is located in the 3rd time zone east of Greenwich. And on the Kremlin clock every time it will be 3 hours more than in Greenwich.
Geographically, there are only 24 time zones. But the local time in different cities does not always correspond to the "geographic" one. For example, in Russia a single time is set for each subject. But what if it is geographically located in several time zones? In this case, it is conventionally referred to one belt, the administrative one. Therefore, to accurately determine the time on Earth, a special map of time zones is needed, where it is precisely indicated which correction is valid in each of the territories. Therefore, in fact, there are more belts, or, as they are called in English, UTC. In some, not even a "round" time is accepted. For example, India is at UTC + 5: 30. With the help of simple calculations, it turns out that when it is midnight in Moscow, in India it is already half past three in the morning.