This issue came up in both AS and A2 classes this week. Even professional publications meet difficulties deciding on a rule in some cases, and there's disagreement at the top.
This doesn't, of course, mean you can ignore all rules of apostrophes. ;)
A sign of the Times's?
http://www.grammarphobia.com/blog/2011/11/times.html
A sign of the Times's?
http://www.grammarphobia.com/blog/2011/11/times.html
