The decan stars — and the star calendars in general (mainly PM 5999)

The Egyptian star calendars are a very interesting aspect of Ancient Egyptian culture. They are also frequently referred to as star clocks, but I find this a very unfitting name as we generally think of clocks as something mechanical; these "clocks", however, have nothing mechanical about them and instead function more similarly to what we would call a "calendar". An ideal star calendar would consist of 36 vertical columns, each one of them depicting one of the ten day long weeks of the Ancient Egyptian calendar system. Due to the Egyptian weeks differing in length from ours, they are often referred to as Dekade (decade) instead (especially in German, it seems). Every one of these columns is further divided up into twelve rows and every row includes the name of one of the decan stars (Baktiu) which are little star constellations; the start of a new week is indicated by the rising of a new Baktiu which results in the names of the Baktiu rising vertically upwards on the calendar (thus, if a Baktiu is at the very bottom of a column during one week, it will become the penultimate one in the following week). New constellations will be shown at the bottom of a column and a new constelltion becomes visible in the night sky, an old one disappears (i.e. the one at the very top of the column).