Explain what you understand by BC and AD and give an example to show how we calculate the number of years between a date in BC and one in AD.
The Correct Answer and Explanation is:
Correct Answer:
BC stands for Before Christ, and AD stands for Anno Domini, which is Latin for “In the year of our Lord.” These terms are used to label or number years in the Gregorian calendar. BC refers to the years before the birth of Jesus Christ, while AD refers to the years after his birth.
To calculate the number of years between a date in BC and one in AD, the two values are added together, subtracting 1 because there is no year zero in the calendar system. For example, to find the number of years between 300 BC and AD 200:
300 + 200 = 500
Then, subtract 1:
500 – 1 = 499 years
Explanation
The Gregorian calendar uses two primary eras to denote historical dates: BC (Before Christ) and AD (Anno Domini). The division between these eras is traditionally based on the estimated year of the birth of Jesus Christ. All years before that point are labeled BC, and all years after are labeled AD.
BC years count backward, meaning 500 BC occurred earlier than 400 BC. In contrast, AD years count forward from year 1 AD onward. It is important to note that there is no year labeled zero in this system. The calendar moves directly from 1 BC to AD 1.
When calculating the number of years between two dates, where one is in BC and the other in AD, the numerical values are added together, then 1 is subtracted to adjust for the missing year zero. For example, to calculate the time span between 150 BC and AD 350:
Step 1: Add the BC and AD values → 150 + 350 = 500
Step 2: Subtract 1 for the non-existent year zero → 500 – 1 = 499 years
Therefore, the time span between 150 BC and AD 350 is 499 years.
This system has been widely used in historical dating and is foundational in Western chronology, although modern scholars often use BCE (Before Common Era) and CE (Common Era) as secular alternatives. Regardless of terminology, the method for calculating the time span remains the same.
