As early as 336, Roman Christians observed Christmas on 25 December of the Gregorian calendar, and Eastern Christians observed Christmas on 25 December of the Julian calendar (which corresponds to 7 January of the Gregorian calendar). The Christian Council of Tours of 567 established Advent as the season of preparation for Christmas, as well as the season of Christmastide, declaring "the twelve days between Christmas and Epiphany to be one unified festal cycle", thus giving significance both to 25 December and to 6January, a solution that would "coordinate the solar Julian calendar with the lunar calendars of its provinces in the east".