A date, a mark, a beginning. A common year 44 BC. The Julian calendar preceded the Gregorian calendar which didn’t start until 1582. The Islamic calendar started in 622 CE and that would be 666 of the Julian calendar which was in effect at that time. The Hegira marks the beginning of Islam.
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.