In honor of yesterday’s celebration of fellow fathers, I am reposting a link to the post I wrote last year about the puzzling apostrophe in Father’s Day. Or is it Fathers’ day? This page is the most visited on my blog with over 200 hits this week alone (a record for me!), and has sparked a lively set of comments. Do add yours!
For the record, I spent a wonderful Father’s Day (my preference) playing with my son at the shore (not the “beach” or the “coast,” by the way in these parts) and I am now busy revising my new grammar textbook, due out some time next year. More blog posts coming soon, I hope.
Nigel Caplan 
As it is a day that recognises all fathers, surely it has to be fathers’ day – particularly if one is speaking in general terms about fathers’ day. If however, it is your father’s day, and his day alone, it would be father’s day. How could it be his day alone though? (Perhaps his birthday?) But, quite simply, fathers’ day it isn’t father’s day and his day alone. It is to recognise fathers all over the world. So, Dad, Happy Fathers’ Day! Your Dad may be one in a million but there are millions of fathers out there! That’s my take on it….
The New Oxford Style Manual says that it is Father’s Day (capital letter, apostrophe before the s)