Before the U.S. mourned the tragic events of September 11, 2001, the Copts had been commemorating that day as the start of their New Year for hundreds of years, as it happens to coincide with the Coptic New Year according to the Coptic calendar (except that it falls on September 12th when there is a leap year, as it does this year).* Interestingly, the Copts have been associating that day with remembering fallen heroes well before it was necessitated by the recent attacks on the U.S.
The Coptic calendar is the Egyptian calendar of antiquity, still in use today by the Coptic Church. Year one of that calendar was reset to remember the day that the infamous persecutor of Christians, Emperor Diocletian, ascended to his throne and embarked on his empire-wide rampage against Christians, of who so many were Egyptian (as the early church historian and bishop Eusebius attests). Since changing the calendar’s year one date, each year has been called “The Year of the Martyrs,” (Anno Martyrum) just like in modern times we refer to each year as “The Year of the Lord” (A.D. – Anno Domini) (where it was attempted to mark year 1 as the year Christ was born, when in fact it appears based on recent scholarship He was born a few years before that, but I digress).
To figure out what Coptic Year we are in, it is a simple matter of subtraction.
From January 1st until the Coptic New Year
= CURRENT GREGORIAN YEAR – 284
(Example: January 1st, 2015: 2015 – 284 = 1731 A.M.
On and after the Coptic New Year (Sept 11 or 12) until January 1st
= (CURRENT GREGORIAN YEAR – 284) + 1
(Example: September 12, 2015: 2015 – 284 = 1731 A.M. + 1 = 1732 A.M.
For more on the Coptic Calendar, go here: http://orthodoxwiki.org/Coptic_Calendar
* For further clarification: Coptic leap years precede the Gregorian Calendar leap year. So, for example, September 10th, 2015 corresponded to what would normally be the last day (the 5th of Nisan) of the of the last Coptic month (the month of Nisan) of the Coptic Year 1731, however because it was a Coptic Leap Year in 1731, an additional day was added, so that September 11th, 2015 corresponds to Nisan the 6th. Accordingly, the following Gregorian Calendar Leap Year is in 2016. Thus, whenever there is a Gregorian Leap Year, the Coptic year (1731) preceding the Gregorian Leap Year (2016) is also a leap year.