The paper offers a refutation of the annalistic dating and a new analytical dating of the time of capture of Polotsk by Vladimir Svyatoslavich, the prince of Novgorod on the Volkhov, and his subsequent marriage to Rogneda, the daughter of the Polotsk prince. Proceeding from available at our disposal reliable dates, it is necessary to think that this event took place in 975—977. This article offers a specification of the date of birth of the second son of Vladimir and Rogneda, Jaroslav – in the interval from 20 (21).02.977 to 19 (20).02.978. Based on a number of indirect data, this interval can be narrowed down to 01.01 — 19 (20).02.978. Thus, this example once again shows that the dates of the events of the 10th century used in historiography, taken from the early chronicle writing, are unreliable. Moreover, in a number of cases, including the one considered in this paper, the time interval between the events is also unreliable, which is quite natural for the historiographical narrative based on the mythopoeic tradition of the Rus’ people who were unfamiliar with writing and had no calendar.