The process of mass Christianization and the use of the official language and the Julian calendar in the administrative offices of local authorities influenced heavily the traditional calendar of the Chuvash people. First of all, the names that denoted the months of the transition period, as well as the name of the main Chuvash rite at the vernal equinox – Kalam, were subjected to semantic transformation. Prior to mass Christianization of the Chuvash people, their calendar year began with the month of norăs / nurăs. This term, along with the concept of a 5-day week, was borrowed from the neighboring Iranian language no later than the 4th–8th centuries AD. Before this period the ancestors of the Onoğurs-Bulgar could name the first month of the year as having the meaning «head month [of the year]» and have, like all Proto-Turkic, a 3-day week. The latter is well reflected in the rules for dividing individual parts of moon phases in the Onoğuro-Bulgar calendar, as well as in a 9-day division of moon phases in the calendars of the Chuvash, the Tuvinians and some other Turkic peoples. Number 9 expresses the main idea of the harmonious unity of the three forces of the universe: the Sky (the Sun), the Man from the middle world and the Earth, where the remnants of his ancestors are. The chronotope of Kalam ritual complex reflects the universal idea of «dying «and «resurrecting» nature. The complex was formed on the basis of the ancient cult of the Sun among the proto-Turks, who associated the year (in the meaning of a «warm season») only with the summer sun. With the development of cattle breeding and the emergence of the concept of a two-season (summer and winter) calendar year, the idea of its beginning also changed. The Chuvash, like other Turkic peoples, divided the months into two groups: summer months and winter ones. Later on, the ancient Turks began to mark transition periods from one season to another. The ancient Turks understood summer and winter as the time of heat and frost «birth and death». Sĕren rite, which originally symbolized treating and seeing off the ancestral spirits, gradually transformed into the agricultural festivals Akatui (sĕren) and Sabantui «plow wedding».