Every so often, I see the phrase “Valentines Day” pop up. I saw it today in fact, and it prompted me to write this short post.
The holiday that occurs on 14 February every year is written as Valentine’s Day. Notice the apostrophe.
The holiday is originally a Christian feast day — and still is in some churches — named after early Christian saints named Valentine. Because it is the day of Valentine, we refer to it in the possessive.