Synaxarion, the church book, was used in St. SofiaЃвs church in the Crimean city of Sudak from the XII to the XV century. On the margins of the book pages priests made notes to register then contemporary events. Those notes were located near calendar dates of Synaxarion which coincided with dates of the events and, besides, were followed by add-up chronological elements (year numbers, days of the week, elements of the Easter reckonings). Research of chronological entries of Synaxarion showed that the majority of them were calculated by years of a Constantinople era of chronology, and those years began with September (from 5509 B.C.). One of addup notes (‡‚ 10) pointed out December 26, 6747 (1238) as the date of the Mongolian Batu-KhanЃfs troops appearance at the city walls. Comparing that date with the information of the Russian chronicles (first of all, with data of the Pskov 1st Chronicle) we may suggest the following succession of events: December, 1238.the invasion of Mongols into the Crimea; March 5, 1239 . seizure of Pereyaslavl-Russian by Mongols; on October 18, 1239 . the seizure of Chernigov; winter of 1239.1240 . MongolsЃf campaign to the Mordovian land.