We often hear this question… When can I send Christmas greetings? Actually, there is no strict rules on this.
But probably… most people aim for beginning to around the 20th December. (If sent by email, you could leave it closer to Christmas.)
Be careful: the spelling of “X’mas” is wrong! “Xmas”, without the apostrophe is OK.
But personally we like to write the word “Christmas”, it sounds more proper and has a better feel.
Don’t forget that the first letter C must be capital 😉 🙂