Islam has it's own dating system, which starts the history clock at the time of Muhammed's (May Peace Be Upon Him) trip to Mecca in 632 A.D., soon thereafter to begin the eventual wholesale slaughter, enslavement, mutilation, or at least disenfranchisement of those Christians throughout the Middle east who refused to convert.
It's also the year 5764 on the Jewish Calendar...I don't know that there is an accepted abbreviation, though I understand they call it the "year of the world" which I suppose would be latinized to Anno Mundi and abb. "A.M.", which could cause humorous incidents:
"The excavation revealed that primitive pumps were in use at the wells of Beersheeba as early as 845 A.M."
"Wow, and it's only 9:05 now!"
]The Iranians [Persians] who controlled the Persian Empire for hundreds of years and were slaughtered by Muslims were not Christians, but Zoroastrians.
I've always wondered what year people said it was during the time before christ. Obvioulsy they weren't counting backwards.