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The Importance of Dates

In history, we use dates to help us find cause-and-effect relationships between human actions. In brief, later actions cannot influence earlier actions, so if we know which thing came first, we can rule out the later one as a cause of the earlier one.

Be careful though--just because something occurred first, it did not influence everything that followed. For example, my grandmother died in 1967, and Newt Gingrich became Speaker of the House in 1994, but there is no reason to think that my grandmother's death was the cause. On the other hand, Adolf Hitler lived through Germany's loss in World War I (1914-1918), and later led Germany into World War II (1939-1945). Historians agree that in this case, the earlier event (Hitler's experience during WWI) helped to cause the other (Hitler's leadership of Germany into WWII).

CE and BCE

Since there is no agreement on when time began, Christian Europeans adopted the convention of recording dates in terms of whether they occurred before or after the beginning of the year of the birth of Jesus Christ. Christians assign the YEAR ONE to the year of Jesus' birth. Muslims do the same thing, only they use the year of Mohammed's return to Mecca. Nowadays, historians believe that Europeans of the Middle Age got the date of Jesus' birth wrong, but nevertheless, we continue to use the system they devised. NOTE: The abbreviations "BCE" (Before Common Era) and "CE" (Common Era) have replaced "BC" (Before Christ) and "AD" (Anno Domini; i.e. "Year of our Lord") respectively.

Assuming that our starting point is the YEAR ONE (there is no YEAR ZERO), then BCE is the abbreviation used for years that occurred before the YEAR ONE. CE is used on all dates starting with YEAR ONE.

Sometimes, we omit the abbreviation CE if we are only talking about modern history--no one would say that Bill Clinton was reelected in the year 1996 CE, although they could if they wanted to. In all of the notes on this web page, BCE dates are always followed by the abbreviation "BCE" but CE dates only include the abbreviation when there is the possibility of confusion. In other words, if you see a date with neither abbreviation, then you should assume it is "CE."


Since this course covers a long period of time, some of the things we will discuss did not take place on a single day or even in a single year. Consequently, we will refer to things that took place "in the third century CE" or "the second millenium BCE," to give just two examples.

First, a definition--a century is a hundred years. That's the easy part. The slightly tricky part is to figure out which years fall in any particular century. For instance, the year 1997 is part of the twentieth century. So were the years 1941, 1911 and 1999. In other words, all of the years that begin with "19" fall into the twentieth century . . . well, almost. The exceptions are 1900, which is part of the 19th century, and 2000 which is part of the 20th century.

Here's why. The first century CE includes the first one hundred years after the first minute of YEAR ONE. In other words, if YEAR ONE began at midnight of January 1, YEAR ONE, then the last day of the first century was December 31, 100. The first century CE includes everything between those two dates.

In a similar fashion, the second century CE began on January 1, 101 and continued until December 31, 200. The twentieth century CE began on January 1, 1901 and ended on December 31, 2000. (Don't be fooled by media reports that New Year's Eve 1999 was the end of the millenium--it may have been true for party-goers, reporters and merchandisers, but not for historians.)

Using the same system, we can calculate the beginning and ending dates for the first century BCE . It must have ended on December 31 of the year before YEAR ONE, and begun exactly one hundred years earlier. If we call the year before YEAR ONE "1 BCE," and the year before that "2 BCE," and so on, then the first century BCE began on January 1, 100 BCE and ended on December 31, 1 BCE.

Here are some examples:

In general, if you know the year, you add 1 to the first two digits to get the century, unless it ends in double-zero (00). Thus, 1997 is in the 19+1 century, or the 20th century. 1800 is in the 18th century.


A millennium equals 1000 years (the plural is millennia). We calculate the beginning of each millenium in the same way as centuries, so for example, the 3rd millennium BCE includes all of the dates between January 1, 2001 BCE and December 31, 3000 BCE.

We are currently living near the beginning of the third millennium CE , which began on January 1, 2001. The first millennium CE included the years from 1 to 1000 CE, and the second millenium CE included the years from 1001 to 2000 CE.


Return to the HIS101 syllabus or the HIS102 syllabus.