Gregorian calendar It also specifies its epact relative to 1 January, in contrast with the Julian calendar, which specified it relative to 22 March. The old date was derived from the Greek system: the earlier "Supputatio Romana" specified it relative to 1 January. During the period between 1582, when the first countries adopted the Gregorian calendar, and 1923, when the last European country adopted it, it was often necessary to indicate the date of some event in both the Julian calendar and in the Gregorian calendar, for example, "10/21 February 1750/51", where the dual year accounts for some countries already beginning their
Ramadan (calendar month) entire month and the gates of Hell (Jahannam) would be closed. The first day of the next month, Shawwal, is spent in celebration and is observed as the "Festival of Breaking Fast" or Eid al-Fitr. The calendar is a lunar calendar, and months begin when the first crescent of a new moon is sighted. Since the Islamic lunar calendar year is 10 to 11 days shorter than the solar year and contains no intercalation, Ramadan migrates throughout the seasons. The Islamic day starts after sunset. The estimated start and end dates for Ramadan, based on the Umm al-Qura calendar of