You use apostrophes primarily to indicate ownership–This is B.’s car–or to indicate a contraction–She won’t mind if we take it for a drive.
You never use an apostrophe to make a word plural. Not even a proper noun. You can go to the Smith’s house–the house owned by the family Smith. You can even go to the Smiths’s house–the house owned by the Smiths. But you cannot go hang out with the Smith’s. No. You cannot. Yes, it’s confusing because you could go hang out at the Smith’s, leaving ‘house’ implied. But unless there’s some object–obvious or implied–you cannot use an apostrophe. Apostrophes cannot make things plural.
Do not, no no no no no, use an apostrophe after a date. It is just 1960s or 1800s or 1490s. A date cannot own something and I cannot think of a way to use a date in a contraction, so just no, don’t do it.
Now, when it comes to pronouns, you don’t need an apostrophe to indicate ownership. This means even “it.” The kitten opened its eyes. (The kitten [it] has eyes; no apostrophe needed on the ‘its’.) It’s so cute. (This “it’s” is a contraction–it is so cute.) So, unless you’re trying to make a contraction, just use ‘its.’
The real question is: Who can make the difference between “affect” and “effect” obvious in a simple way?