An apostrophe is typically interchangeable with a single-close-quote, but it can be different within a more specialized font face. One could be forgiven for using a neutral single quote in a pinch (an abhorrent anachronism of mechanical typewriters).
I think when referring to the entire group of years that make up an entire decade (and thus indicating plurality), the proper form is 1920s without the apostrophe because you are essentially stating the following: "all the years that make up the decade which begins with the year 1920" when you use this construction. When trying to indicate that something belongs to a particular decade, you may ...
grammatical number - Is an apostrophe with a decade (e.g. the 1920’s ...
I will disagree, and support the position that an apostrophe indicating possession is now not necessary in such phrases - where the plural is being used. So two weeks notice and two years experience are acceptable, however in the singular, the apostrophe is still required: one year's experience, or one week's notice. I base this on the notion that an apostrophe at the end of a word (two years ...
While you're in school you can spell it men's (also women's, children's, oxen's, sheep's, deer's) with just plain old Apostrophe-S. You can't tell the singular from the plural possessive in speech, so there's no reason to do it in writing, either. So after you get out you can just omit the apostrophe like we do in speaking and write mens room the way it's pronounced. Most native speakers don't ...
apostrophe - Is it "men's" or "mens'"? And what's the rule? - English ...