Finally created in the 16th century AD. e. and the chronology and history of the ancient and medieval world accepted today appears to contain major errors. This was understood and discussed by many prominent scientists over a long period of time. But constructing a new, consistent concept of chronology turned out to be a difficult task. Starting in 1975, a group of mathematicians, mainly from Moscow State University, took up the development of this problem. Interesting results were obtained, published both in scientific periodicals and in the form of separate monographs. We emphasize that the new concept of chronology is based, first of all, on the analysis of historical sources BY METHODS OF MODERN STATISTICS and extensive COMPUTER CALCULATIONS. The reader may ask: why did mathematicians take up chronology? After all, it is believed that chronology is a branch of historical science. The fact is that chronology in its essence should relate more to applied mathematics than to history. The purpose of chronology is to correctly order events on a timeline according to the information at our disposal. This problem naturally fits into the area of applications of modern mathematical statistics and information theory. The methods of purely humanities, such as history, are insufficient for solving chronological problems. This book is a brief introduction to the problem.