For some, it’s not a contraction, it’s a possessive pronoun. For others, it’s a non sequitur.
For still others, it’s the typical mistakes that pepper Yahoo! Shine every day.
Grammatically challenged writers confuse its and it’s, and most often use it’s (a contraction for it is or it has) when they should be using its (a possessive pronoun). But Yahoo! writers are, if nothing else, creative in their misuse of English. But few professional writers would write two sentences in such a similar, yet completely wrong, structure to imply that “for some, it’s not Christmas; for others, it’s oysters on the half shell.” Which is true, now that I think about it.
(What the writer really meant: For some, it’s not Christmas until they have a glass of eggnog by a twinkling tree. For others, it’s not Christmas until they dig into oysters on the half shell.)