5,509 B.C.

The Byzantine calendar was the calendar officially used by the Byzantine Empire (Eastern Roman Empire)[1] from 988 by Basil II until it was conquered in 1453. It was identical to the Julian calendar except that the names of the months were transcribed from Latin into Greek, the first day of the year was 1 September, and its year one was 5509–08 BC. http://en.wikipedia.org/wiki/Byzantine_calendar
5509 B.C. = year 1 B.E. (Byzantine Era) = Creation of the World This year began on 1 September. An alternative reckoning with a year beginning on 25 March estimated the creation of the world in 5483 B.C.
What makes the date 5509 B.C. remarkable is that it is also the date given to the alphabet of Adam.