Decades and Centuries
Writing about dates in general terms often inspires us to refer to decades and centuries. Admitedly there are many of them, but the rule for them is all the same. When writing of a particular decade follow the numbered date with an "s". Do not use an apostrophe. For example:
The 1950s seem to us now to have been a time of innocence.
However, decades are often refered to without the century. When this happens an apostrophe is used to stand in for the century. For example:
Yet Americans in the '50s saw their share of conflict and strife.
Centuries are treated in the same manner as a decade (that includes the whole date). Thus, we have:
The 300s saw the rise of Constantine and the movement of the capital of the the Empire to the East.
However, note that when a writer refers to a particular century then he or she must use the century number one iteration after the actual date. Thus the 1800s are called the "19th Century" or even "Nineteenth Century". For example:
Perhaps the nadir of the 20th century was 1941 when Pearl Harbor was attacked and the Germans had just launched their invasion of the Soviet Union.
The reason for this seeming aberation becomes obvious when one realizes that the first century was from the year 0 to the end of 99. The second century plays out over the 100s, and so on.
Articles About English Grammar