The Egyptian civil calendar in place by Dynasty V followed regnal eras resetting with the ascension of each new pharaoh. It was based on the solar year and apparently initiated during a heliacal rising of Sirius following a recognition of its rough correlation with the onset of the Nile flood. It followed none of these consistently, however. Its year was divided into 3 seasons, 12 months, 36 decans, or 360 days with another 5 epagomenal days—celebrated as the birthdays of five major gods but feared for their ill luck—added "upon the year". The Egyptian months were originally simply numbered within each season but, in later sources, they acquired names from the year's major festivals and the three decans of each one were distinguished as "first", "middle", and "last". It has been suggested that during the Nineteenth Dynasty and the Twentieth Dynasty the last two days of each decan were usually treated as a kind of weekend for the royal craftsmen, with royal artisans free from work. This scheme lacked any provision for leap year intercalation until the introduction of the Alexandrian calendar by Augustus in the 20sBC, causing it to slowly move through the Sothic cycle against the solar, Sothic, and Julian years. Dates were typically given in a YMD format.