The Codex by Tomasz Strzępiński, located in the Gniezno cathedral library, contains, among others, calendar with obituary entries. Over a hundred years ago, the entries from this calendar were published without corrections and with errors. The calendar was written in the years 1437-1440. Its creation is related to Tomasz Strzępiński's participation in the work of the Basel Council Commission for Calendar Reform. Later, obituaries with the names of 32 Krakow canons who died in the first half of the 15th century were added to the calendar. This circumstance clearly indicates the Krakow cathedral as the place where these entries were made. The obituaries are dated to the years 1440-1460, i.e. from the time of the stay of the owner of the codex, Tomasz Strzępiński, in Krakow - first as a canon, then as a bishop. They allow us to precisely determine the dates of death of several outstanding figures of Polish political and cultural life of that time. In 1460, based on Tomasz Strzępiński's will, the codex was sent to Gniezno, where it remains to this day.