I think most people agree on the basics of using an apostrophe: 1. for possession and 2. to show letters were left out.
The controversy seems to raise its grumpy head when it comes to dates. Some people were taught that using apostrophes (1870’s) is correct, and others were taught that it is horribly, horribly wrong (1870s).
Here’s the argument in a nutshell:
From what I can see, the No Apostrophe Rule is technically correct for dates (at the moment – grammar rules change, so I generally go to Purdue OWL if I want to check).
When it comes to dates like “the nineteen hundreds,” I totally get the argument. “1900” is “nineteen hundred,” so adding an “s” by itself makes sense. It’s not possessive, and there are no letters missing – no apostrophe. Got it.
My question is about dates like “the nineteen twenties.” “1920” is not “nineteen twenties” – it’s “nineteen twenty.” That means adding an “s” gives you “nineteen twentys,” which is not the same thing at all. In this case, there are letters missing. The “y” is a problem, yet of the two, the apostrophe makes more sense in this situation.
But… rules are rules, right?
Does it make perfect sense? No. It’s English. Could it change in the future? Yes. It’s English. Will people understand either way? Yes. Will you get made fun of online if you do it wrong? Maybe.
Let’s be honest. So long as putting an apostrophe with a date is the only apostrophe rule you break, you’ll probably be just fine.