The Armenian calendar was the main calendar used in Armenia during the medieval period. The year in this calendar is exactly 365 days long, divided into twelve months of thirty days each, plus five extra days that are called ""aveleacʿ"" in the Armenian language, which are not a part of any month. The first year in the Armenian calendar is equal to the year 552 AD in the Gregorian calendar. This calendar was mainly used in the medieval era, but is also used in modern times by some Armenian nationalists.