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.
In A.D. 352, tables compiled by Andreas of Byzantium were introduced in Armenia to determine the religious holidays. When those tables exhausted on 11 July 552 (Julian Calendar), the Armenian calendar was introduced.
Year 1 of the Armenian calendar began on 11 July 552 of the Julian calendar. Armenian year 1462 (the first year of the second cycle) began on 11 July 2012 of the Julian calendar (24 July 2012 of the Gregorian calendar).
An analytical expression of the Armenian date includes the ancient names of days of the week, Christian names of the days of the week, days of the month, Date/Month/Year number after 552 A.D., and the religious feasts.
Years are usually given in Armenian numerals; which are letters of the Armenian alphabet preceded by the abbreviation ԹՎ for t’vin, meaning "in the year." For example, ԹՎ ՌՆԾԵ, which means "the year 1455."