Spotted in the NZ Herald today:
Misuse of the apostrophe in the event of a word ending in an ‘s’ must be the single most common grammatical blunder in the English language.
An apostrophe denotes possession not pluralisation. It is used to identify a possessive noun, for example:
Michelle’s hat (The hat that is owned by Michelle)
If the possessive noun is in the plural, then the ‘s’ is not required. For example:
Two weeks’ notice (The possessive noun is ‘weeks’, which is already in the plural)
It’s reasonably basic grammar, but for some reason so many people, including professional writers, still get struck down by apostrophic mania.
There seems to be no cure.