The plural of Christmas is Christmases.
Christmas is an annual festival observed by Christians to celebrate the birth of Jesus Christ.
"Christmas" can be used in the plural form to refer to specific instances or occurrences of the holiday.
For example, "Two Christmases ago, I received many gifts." In this sentence, the word "Christmases" is being used to refer to the specific instances of the Christmas holiday that occurred two years in the past.
It's worth noting that the word "Christmas" is usually used in the singular form, as it refers to a single holiday that occurs annually. However, it can be used in the plural form to refer to specific occurrences of the holiday.
The plural for Christmas is formed in English by adding the suffix -es to the end of the word.
Christmas's is used in English but never to denote a plural.
Christmas's is used in the possessive sense. Eg. 'This Christmas's tree will not be quite the spectacle as last Christmas's.
As a rule, English words never use an apostrophe to form their plural.
Here are some example sentences to illustrate the difference between "Christmas" and "Christmases":
For some Japanese people, Christmases spent eating chicken at KFC has become a tradition!