A historian can establish the laws of the development of society only by studying specific historical events in their chronological sequence. However, it is not always possible to establish a chronological sequence of historical phenomena without special research, since a number of facts of ancient, middle, and sometimes new history are difficult to accurately establish the time in which they were performed. In addition, historical events of the distant past are recorded by sources in the dates of their modern chronology and calendar. These dates are subject to translation into modern chronology. From the need to establish the time of historical events and their sequence, an auxiliary historical discipline was born - chronology.