Russian Empire
Though the Empire was only officially proclaimed by Tsar Peter I following the Treaty of Nystad (1721), some historians would argue that it was truly born either when Ivan III of Russia conquered Veliky Novgorod in 1478, or when Ivan the Terrible conquered the Khanate of Kazan in 1552. According to another point of view, the term "Tsardom", which was used after the coronation of Ivan IV in 1547, was already a contemporary Russian word for empire.
Russian Primary Chronicle
The historical period covered in the "Tale of Bygone Years" begins with biblical times, in the introductory portion of the text, and concludes with the year 1117 in the "Chronicle's" third edition. Russian philologist and founder of the science of textology, Aleksey Shakhmatov, was the first one to discover early on that the chronology of the "Russian Primary Chronicle" opens with an error. The "Chronicle" has it that “In the year 6360 (852), the fifteenth of the indiction, at the accession of the Emperor Michael, the land of Rus’ was first named.” However, John Skylitzes' accounts of the Byzantine history show that Emperor Michael III did not begin his reign in 852 but rather a decade earlier, on January 20, 842. Because of the work's several identified chronological issues and numerous logical incongruities that have been pointed out by historians over the years, the "Chronicle's" value as a reliable historical source has been placed under strict scrutiny by the contemporary experts in the field (see “”).