The year starts on the Feast of Neyrouz, the first day of the month of Thout, the first month of the Egyptian year. For 1901 to 2098 it coincides with the Gregorian Calendar's 11 September, or 12 September before a leap year, but for any year, it coincides with the Julian Calendar's 29 August, or 30 August before a leap year. Coptic years are counted from 284 AD, the year Diocletian became Roman Emperor, whose reign was marked by tortures and mass executions of Christians, especially in Egypt. Hence, the Coptic year is identified by the abbreviation A.M. (for "Anno Martyrum" or "Year of the Martyrs"). The first day of the year I of the Coptic era was 29 August 284 in the Julian calendar. Note that A.M. abbreviation is also used for unrelated calendar eras (such as the Byzantine and Jewish calendar epochs) which start at the putative creation of the world; it then stands for "Anno Mundi".