Adoption of the Gregorian calendar Julian to the Gregorian calendar. For example, in the article "The October (November) Revolution" the "Encyclopædia Britannica" uses the format of "25 October (7 November, New Style)" to describe the date of the start of the revolution. Other countries of eastern Europe, most notably Eastern Orthodox countries, adopted the Gregorian calendar in the 1910s or early 1920s. The last country of Eastern Orthodox Europe to adopt the Gregorian calendar for civil purposes was Greece, at the time under military administration following the 11 September 1922 Revolution, with Wednesday 15 February 1923 being followed by Thursday 1 March 1923. The Soviet
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