when I want to know something, I call on my favourite pedants.......

[waitingforgodot]

so please don't let me down. I have had a total mind blank.
How do I write Fergus' birthday?
Is it as above or Fergus's birthday?

I am doubting myself hence reason for post

either is fine.

I'd go Fergus's birthday, because you would always pronounce the second s. That's the general rule with apostrophe-s: if you say the s, write it. You can, however, do it without: these are questions of convention rather than correctness.

Agree with AFD.
Fergus' birthday is pronounced Fergus birthday.
Furgus's birthday is pronounced Fergusis birthday.

I prefer the second, but it's personal choice.

So either way is fine. Excellent! Perhaps that's why I was doubting myself. Merci beaucoup xx

NOOOOooooo!!!!!!

it's Fergus's birthday.

Never Fergus' birthday.

Sorry, you're all wrong (I think, I'll go and google to make sure...)

BBC agrees with us

although it does say sometimes one is better than the other to make the meaning clear if spoken - presumably if written it doesn't matter.

Many respected sources have required that practically all singular nouns, including those ending with a sibilant sound, have possessive forms with an extra s after the apostrophe.

wiki agrees with me

here is the wiki page if you can be bothered trawling through it all

Fergus' birthday may be accepted but it doesn't mean it is correct .

But it's the BBC! Not wikipedia!

Oh yes, well, the BBC, that unbiased centre of correctness and high values . Have you seen the mistakes they allow through on their subtitles? I mean, put your trust in that west London brigade of slackers if you like but...

Well I agree with you but wikipedia could be anyone, couldn't it?

What have I started here?!!
Will go grab the popcorn and a chair!

I suspect this is one that's had variant usage for some time - various US style guides seem to disagree.

This is what the MHRA style guide (used for humanities theses in the UK) says:
The possessive of proper names ending in a pronounced -s or -z is formed in the normal way by adding an apostrophe and s:
Alvarez?s criticism, Berlioz?s symphonies, Cervantes?s works, Dickens?s characters, in Inigo Jones?s day, Keats?s poems, Dylan Thomas?s use of language
French names ending in an unpronounced -s, -x, or -z also follow the normal rule and take an apostrophe and s:
Rabelais?s comedy, Descartes?s works, Malraux?s style, Cherbuliez?s novels
The possessive of names ending in -us also conforms to the normal rule:
Claudius?s successor, Herodotus?s Histories, Jesus?s parables, an empire greater than Darius?s
However, the possessive of Moses and of Greek names ending in -es (particularly those having more than two syllables) is usually formed by means of the apostrophe alone:
under Moses? leadership, Demosthenes? speeches, Sophocles? plays, Xerxes? campaigns

brilliant!
I get it now! Thanks Habbibu

You're welcome - bear in mind that this is just the decision taken by the editors of this particular guide.

There are far fewer "rules" in English language than people think - or like to think!