A calendar era is the year numbering system used by a calendar. For example, the Gregorian calendar numbers its years in the Western Christian era (the Coptic and Ethiopic churches have their own Christian eras, see below). The instant, date, or year from which time is marked is called the epoch of the era. There are many different calendar eras. The first "universal" calendar era not dependent on the ruling monarch was introduced in the 4th century BC, with the olympiad, counted from the first Olympic Games in 776 BC.