Century leap year was introduced in 1582, but was adopted by various countries over several centuries, with the result that some countries still used the older Julian calendar while others used the Gregorian calendar. Dates prior to 1582 are generally calculated using the Julian calendar, and different countries have different conventions about dates between 1582 and their adoption of the Gregorian calendar. (See, for example, Old Style and New Style dates.) Century leap year In the Gregorian calendar, a year ending in "00" that is divisible by 400 is a century leap year, with the intercalation of February 29 yielding 366 days instead
Egyptian calendar Egyptian calendar The ancient Egyptian calendar was a solar calendar with a 365-day year. The year consisted of three seasons of 120 days each, plus an intercalary month of 5 epagomenal days treated as outside of the year proper. Each season was divided into four months of 30 days. These twelve months were initially numbered within each season but came to also be known by the names of their principal festivals. Each month was divided into three 10-day periods known as decans or decades. It has been suggested that during the Nineteenth Dynasty and the Twentieth Dynasty the last two