You have already written holiday cards and are now ready for dispatch, but you decide to, first, double-check your use of capitalization. So, do you capitalize Merry Christmas? Well, yes!
The reason is, unlike the word holiday, which does not refer to any officially elected day but rather the entire season, Christmas Mass is the official name of a characterized religious holiday. So, provided you are writing it as a proper noun, and as such refers to a specific day, Merry Christmas capitalized, should appear on all your cards.
Shortening Holiday Terms
When you combine the words such as day and eve with the holiday name, make sure you capitalize Christmas and the accompanying words. Note that shortening the holiday name does except it from capitalization because they still refer to specific events in the region’s history. In the same way, always capitalize proper holiday nouns such as New Years’ Eve, Thanksgiving (celebrated in The United States), Halloween and Boxing Day (observed in the United Kingdom) and other similar terms.
When Not to Capitalize the Accompanying Words
When, for instance, you are referring to an individual being merry on that particular day you don’t capitalize the complimentary word. So, telling someone to have a happy Christmas (without caps in the adjective) is grammatically correct. Your use of the adjective joyous is not unique since you could as well have chosen any other words with the same meaning such as happy, merry, festive, sober and so forth. However, Christmas has to be in caps because even in the sentence it refers to a designated occasion.
Merry Christmas is always capitalized because Christmas points to a particular day and hence is a proper noun. The accompanying adjective is also a part of the command. So, make sure you get it right any time you use it.