This book from the series "What Is What" tells about , How Humans Invented and Improved Time-Accounting Systems Where and when did the moon appear? Lunar and solar calendars , What calendars are used by residents of different countries? The History of , [CM the Gregorian calendar. 122444444444444444444444444444444444444 Recently, the 20th century has been replaced by the 21st century, and in addition, a new, third millennium has come .. [Dt.] [ ] How do we know that the new year begins on January 1, and not on March 1 or September 1? And that the XXI century began, and not some other? Calendar is one of the most important inventions of mankind. As is often the case with inventions, the history of the calendar is far from simple, everything in it happened. It begins in ancient times, when it became clear to man that there are strict patterns in the movement of time, and this movement itself must be taken into account in some way. After one day comes another.... Warm months are replaced by cold . People also noticed that the Sun rises above the horizon every day not at the same point as the day before, but after a certain number of days the whole cycle repeats. And the Moon, it turned out, revolves around the Earth according to a strict schedule .. On the basis of astronomical observations, different peoples created their own time frames: there were calendars in ancient Egypt, and in ancient China, and the Mayans, and the Sumerians. They were “tied” to the movement of either the Sun, or the Moon, or to the movement of both. Which of the ancient calendars was destined to become the basis of our modern? Why is it now called Gregorian? When was the countdown from the Nativity of Christ introduced? What calendars are used in Muslim countries and Southeast Asian countries? This new book from the What Is What series tells about all this and much more "What Is What" is a series of thematic encyclopedias published from 1994 to 2001 by the publishing house "Word" and aimed at school-age children. Initially, it was translated materials of a similar German series "Was ist was", but later, as part of the series, the publishing house began to produce works by domestic authors. The abundance of illustrations, fascination, diversity and accessibility of the presentation of the material predetermined the great popularity of the series. "What is What" easy reading - serious knowledge!Other books in the series "What is What":Byzantine Wolves of Heaven. Flags Calendar. Caves of the Cat. Time. Dolls. Butterflies Sculpture. Our Body . Ancient Greeks Ancient myths Myths of Slavs Sun Apes Ancient China . Painting Orbital Stations . Underwater exploration of the Earth Planet Ancient Greece. Trees. Forest. Poisonous plants . Money from Russia . Multimedia and virtual worlds Natural Disasters Mountains Pyramids Museums Travelers . Crusaders Weather. Bees, Bumblebees, Wasps Moors Elephants Fish Birds Ships Gladiators Samurai. Pirates. Water. Bridges . Geographic Maps of the Witch Star. Internet Seven Wonders of the World Predators Nuclear Power Arctic and Antarctic. Indians Horses Dinosaurs Ancient Russia . Moscow Rus Revival . Mysterious Treasure Phenomena . Tropical Forest