Although time does not have a beginning and an end, when it comes to the study of history it is necessary to define an anchor point on the timeline as a starting point for the counting of years. The discussion of calendars in Lecture 7 will show that different civilizations use different ways to divide time into eras.
Many civilizations used more than one anchor point, for example the first days of the reigns of successive emperors, which leads to a succession of several eras and identification of dates exclusively through positive numbers ("the fifth year of the reign of Emperor Tai Zong of the Tang dynasty"). The Meso-American calendar was based on a zero point so far back in time (at 3113 BC) that for all practical applications the identification of dates also invoked only positive numbers.
The European civilization uses two eras, BC ("Before Christ") and AD ("Anno Domini", Latin for "in the year of the Lord"). This system, which leads to a positive (forward) count for the AD era and a backward (negative) count for the BC era, has been widely accepted today.
Some authors argue that in today's global village the terms BC and AD are offensive to civilizations that are not based on Christianity; they propose the terms BCE ("before the common era") and CE ("common era") instead. The logic behind this argument is interesting to say the least. Giving the date of Julius Caesar’s assassination as 44 BCE instead of 44 BC does not change the fact that it still imposes the calendar of the European civilization on the world as the "common" era. Rather than imposing the Christian era as the "common era" on all civilizations, I prefer to continue with the European tradition and use BC and AD to reflect my European upbringing. Whether my lectures will offend other civilizations will not be decided by the use of BC or BCE but by their content.