When I was a boy going to grade school, way back when dinosaurs roamed the earth, tramping five miles to and fro, somehow uphill both ways, they taught us English grammar. We parsed sentences and memorized irregular verbs til the cows came home. They pounded rules into our fertile young minds, then just as hard they pounded in the exceptions.
One of the rules that was driven home was the concept of possession and the apostrophe S. To indicate possession an apostrophe S is added as in Bill’s desk or Mary’s car. The exceptions were words that already ended in S or X, such as Alex’ shoes or Gus’ cookies. These exceptions were pronounced as if there was no apostrophe: I really enjoyed Gus cookies, not GusES.
All was well until some kid went to London and visited St. James’s Park, located a mere jeweled-orb’s throw from Buckingham Palace. This certainly put a spanner in the works.The recent release of the film Bridget Jones’s Baby has given me pause for thought. So I did a little research. According to Mignon Fogerty, Grammar Girl at QuickandDirtyTips.com it is all a matter of choice of style. The Associated Press Stylebook recommends the method that I am familiar with, no added S, just an apostrophe, while Fowler’s Modern English Usage suggests using the additional S.
That is fine and dandy for the written word, but when it comes to saying these phrases we were taught not to emphasize all those S sounds. So while I would write the name of the film Bridget Jones’ Baby I would pronounce it Bridget Jones Baby.
Ain’t English fun?
DCMontreal 
I’ve always used the additional S… I don’t know why, but I do know it’s a choice I made. (PS: If you have not read it, I highly recommend “Crazy English” by Richard Lederer for some more crazy fun!) : )
I agree with you. I have always put an apostrophe after my name for my possessions, as in, Chris’ notebook.
It is dumb english to add a second S when the noun or pronoun end with an S already.
My last name is McGuinness and I would just put an apostrophe after it.
Thank you.