According to the New York Times style guide, official NYT style is to write 1960's for the plural. The motivation is that in all-caps headlines, 1960S is hard t

According to the New York Times style guide, official NYT style is to write 1960's for the plural. The motivation is that in all-caps headlines, 1960S is hard to read, so they used an apostrophe. For consistency, they used this in body text too. (They may have changed the style guide away from this recently, though.) The larger point is that many grammar things I thought were matters of right and wrong are actually matters of style. (Just sharing a random factoid stuck in my brain, not trying to start a grammar flame war.)