Singular possessive adds an apostrophe s, regardless of the letter the word ends in, barring exceptions like "its".
While it's true that it can be acceptable to do the alternative depending on where you go, the fewer silly rules we have in grammar, the better.
Quote:I did earlier.
Darius' is plural meaning 2 or more Darius (If Darius was a last name it could be John Darius and Martha Darius) own something.
Darius's is singular meaning Darius owns something.
Both ARE correct IF (and I can't stress this enough) they are used in the proper situation. Since there is only one (thank god) Darius it has to be Darius's. Darius' makes zero sense.
Saying you can use either is lazy at worst, and ignorant at best.
Let us remember Office Space:
"I got a meeting with the Bobs in a couple of minutes."
Quote:Originally Posted by The Chicago Manual of Style (16th Edition), 7.15The possessive of most singular nouns is formed by adding an apostrophe and an s. The possessive of plural nouns (except for a few irregular plurals, like children, that do not end in s) is formed by adding an apostrophe only. For the few exceptions to these principles, see 7.19-21. See also 5.19.