Adoption of the Gregorian calendar for secular use occurred in Eastern Orthodox countries as late as the 20th century and some religious groups in some of these countries still use the "old style" (O.S.) Julian calendar for ecclesiastical purposes. The Kingdom of Bulgaria changed from the Julian to the Gregorian calendar during the First World War on 31 March 1916, where the next day was 14 April 1916. The Ottoman Empire's Rumi calendar, used for fiscal purposes, was realigned from a Julian to a Gregorian starting on 16 February/ 1 March 1917. The beginning of the year was reset to 1 January starting in 1918.
Intercalary month (Egypt) of the season of Low Water. This month may have had as many as 30 days. According to the civil calendar, the months fell in order with the rest regardless of the state of the moon. They always consisted of 30 days, each individually named and devoted to a particular patron deity, but the year was always followed by an intercalary month of only five days. Owing to the lack of a leap day, the calendar slowly cycled relative to the solar year and Gregorian date until the Ptolemaic and Roman eras. The period of the intercalary month was considered