section_path: Eras/Past Eras/Era of Martyrs
section_name: Era of Martyrs
paragraph_text: Era of Martyrs
  
  The most important era – once widely used by Eastern Christianity, and still used by the Coptic Orthodox Church of Egypt – was the Era of Martyrs, also known as the Diocletian Era, or the era of Diocletian and the Martyrs, whose first year began on 29 October 328.
  
  Respective to the Gregorian and Julian New Year's Days, 3½ to 4 months later, the difference between the Era of Martyrs and the Anno Domini is 285 years (285= 15×19). This is because in AD 525, Dionysius Exiguus decided to add 15 Metonic cycles to the existing 13 Metonic cycles of the Diocletian Era (15×19 + 13×19 = 532) to obtain an entire 532 year medieval Easter cycle, whose first cycle ended with the year Era of Martyrs 247 (= 13×20) equal to year DXXXI. It is also because 532 is the product of the Metonic cycle of 20 years and the solar cycle of 28 years. It has 13 months in a year.