A beginning. A date is the most common mark on any product sold today. Consider 666 as a mark or a date. What happened in that year? What calendar? The Gregorian started in 1582 or the Julian starting at 44 BC or the Islamic calendar starting in 622? Consider them all.
A Dating Tool
a common year. 666 of the Gregorian calendar, which didn’t start until 1582, will be a different year in a different calendar. The common year for the Julian calendar was 44 BC. 622, the year of the Hijra, would be 666 in the Julian calendar. That does require a calculation and not a count as stated in some bibles.