Write a sentence with a date that shows possession. For example, the sentence "Elvis Presley's movie debut was one of 1956's biggest Hollywood events" needs an apostrophe before the "s."
Follow the date with an apostrophe and an "s." For example, write "1956's."
Omit apostrophes for dates that do not show possession. For example, write, "The 1960s was a decade of change for women's fashion." In this sentence, "1960s" does not indicate possession, instead it indicates a plural number of years.