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
Calendar reform in advance). This calendar has 19 months of 19 days, with an extra 4 or 5 intercalary days added so that the year ends on the day before the next vernal equinox. Lunisolar calendars usually have 12 or 13 months of 29 or 30 days. Some propose to improve leap rules of existing calendars, such as the Hebrew calendar. The Rectified Hebrew calendar uses a more accurate leap cycle of 4366 months per 353-year cycle, with 130 leap years per cycle, and a progressively shorter "molad" interval, intended to replace the 19-year leap cycle and the constant "molad" interval of