The Mothers Day case is exactly the same problem:
See here, from:
http://www.betterwritingskills.com/newsletters /2005-05.txt
"Mothers Day", "Mother's Day" or "Mothers' Day"?
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Well it's Mothers Day in many countries this coming Sunday, so now seems like the perfect time to ask the burning question: Does "Mothers Day" need an apostrophe, and -- if so -- where does it go?
Ask any group of people that question. After the bickering stops, the combatants will have settled into three camps. Let's look at all three in turn.
Choice 1. Mothers Day:
The argument here is that mothers do not own the day, so no possession is involved; thus, no apostrophe is needed. We are describing a day *for* mothers.
Choice 2. Mother's Day:
Here the argument is that the day belongs to one specific mother (yours presumably). So, because possession is involved, "Mother's Day" needs an apostrophe before the "s".
Choice 3. Mothers' Day:
Here the argument is that the day belongs to all mothers
collectively; thus, we need an apostrophe after the "s".
And the winner is?
So, which is it? Well, let me stress that you can make a
reasonable case for all three of the choices, so it comes down to whether you think that ownership is involved or not.
In British English there is an increasing tendency to omit
apostrophes when "for" is implied rather than "of" or "belonging to".
An increasing number of editors of British English publications are thus opting for choice one (no apostrophe) arguing that Mothers Day is a day *for* mothers, not a day belonging to mothers.
US usage, however, seems to