Intercalation (timekeeping) year of 365 days, an extra day ("leap day" or "intercalary day") about every four years, causing a leap year to have 366 days (Julian, Gregorian and Indian national calendars). The Decree of Canopus, which was issued by the pharaoh Ptolemy III Euergetes of Ancient Egypt in 239 BCE, decreed a solar leap day system; an Egyptian leap year was not adopted until 25 BC, when the Roman Emperor Augustus successfully instituted a reformed Alexandrian calendar. In the Julian calendar, as well as in the Gregorian calendar, which improved upon it, intercalation is done by adding an extra day to
Middle-earth calendar the three extra days in every third "yén" (once every 432 years), for an average year length of ≈365.24306 days. In Rivendell, the "loa" began on the spring equinox and was divided into six "months" or seasons, as follows. Five other days, two between "coirë" and "tuilë" and three between "yávië" and "quellë", meant the calendar added up to 365 days. Irregularities were allowed for by adding another three days every twelve years, except the last year of a "yén". The calendar developed by the Men of Middle-earth is called the King's Reckoning, and is in many ways similar to