This post is for my students and for anyone unfamiliar with the method of converting years into centuries.

Fortunately or not, there are certain rules one must follow to achieve proper conversion:

Rule 1: There is no year 0 in the calendar.

Rule 2: All years between 1-100 are I century;

Rule 3: When a year is a three-digit number (101-999), one must add +1 to the first number, e.g year 325, 3 (first number) +1=4, therefore year 325 is in the 4th century (IV);

Rule 4: When a year is a four-digit number (1001-9999), one must add +1 to the first two numbers, e.g the year 1018, 1, and 0 (first two numbers) +1=11, therefore year 1018 is in the 11th century (XI)

Rule 5: Round three-digit years! The first number will give the information about the century, e.g year 700 –> 7 is the first number so 7th century (VII), 500 –> 5 is the first number so 5th century (V);

Rule 6: Round four-digit years! The first two numbers will give the information about the century, e.g the year 1700 –> 17 (first two numbers) so 17th century (XVII);

Rule 7: All former rules apply equally to B.C and A.D years.

Rule 8: Span of the centuries:

A.D. (Anno Domini) start from 01 and end in 00 e.g. 1901 – 2000 = XX century

B.C. (Before Christ) start from 00 and end in 01 e.g. 500 – 401 ends, starts V century;

Some examples:

1st century runs from year 1 to 99.

1st century B.C. = 100 – 1

2nd century runs from 100 to 199.

2nd century B.C. = 200 – 101

A.D. 21st century runs from 2001 to 2099.