Why do some people say "Happy New Years" with an "s" at the end of "years"?

Why do some people say "Happy New Years" (with an "s" at the end of "years")? Here are some examples on Twitter: http://twitter.com/#!/search/%22happy%20new%20years%22

It seems like "year" should be singular, because there is only one new year.

Solution 1:

It's a misspelling^[1] of Happy New Year's, i.e. Happy New Year's Day, where New Year's Day is January first. Or so I've always understood it, anyway.

^{[1] But see comments on this answer.}

Solution 2:

It think it comes from the phrases New Year's Eve and New Year's Day in both it is correct to add the "s". We would not say New Year Eve or New Year Day. This possessive form is erroneously carried over by some to the greeting for the New Year. As pointed out by @FumbleFingers when someone refers to New Year's (without eve or day specified) it implies New Year's Eve.

Solution 3:

Many holidays end up with a possessive on them - Happy Valentines! we'll say, as likely as Happy Valentine's Day, or Happy Saint Paddies! instead of Happy St Patrick's Day. Technically we wish each other the entire New Year happy, not just New Year's Day, but I would never correct someone who said Happy New Years! to me.

If you used "New Year's" in a sentence, rather than in the set phrase "Happy New Years!" I would probably think you meant New Year's Eve, especially in a context like "what are you doing New Year's?" or "we met at New Year's". So don't use it outside that set phrase.