The Armenian calendar is the calendar traditionally used in Armenia, primarily during the medieval ages. The Armenian calendar is based on an invariant year length of 365 days. Because a solar day is about 365.25 days and not 365 days, the correspondence between it and both the solar year and the Julian calendar slowly drifted over time, shifting across a year of the Julian calendar once in 1,461 calendar years (see Sothic cycle). Thus, the Armenian year 1461 (Gregorian & Julian 2011) completed the first Sothic cycle, and the Armenian Calendar was one year off.