No, your computer calendar is not wrong, it is the fifth, not the twenty-fifth. And no, I have not lost it. I am fully aware that tradition states that "Santa" comes on Christmas Eve. At least, modern tradition states that.
I'll spare my readers the long story of Saint Nicholas. Instead, I'll let you read the Wiki article.
When I lived in Germany, we used to celebrate St. Nicholas' Day in our schools as a way of getting a feel for German culture. In the German fashion, we would leave our shoes outside of our classroom door and "St. Nick" would come by and fill them with candy. When I was younger, I figured this was how Santa was able to make it around the world - by staggering his expected arrival, the trip would be way, way easier on the reindeer.
In more practical terms, though, I really like the idea of keeping Christmas and Saint Nicholas separate. I was raised expecting Santa to come on Christmas Eve, and to this day, a part of my family's tradition is to open "Santa's" presents (Yes, he still comes to visit us, and my sister and I still even leave a note and cookies. When you move every couple of years, even silly traditions like these make a new place feel more like home, and I look forward to Santa's visit to my parent's new place this year. Tangent over.) after the stockings, but before any of the other presents (My family also stretches out the gift-opening). But I can't help but feel that something is lost in the merging of the two traditions. While I disagree with the commercialization of any religious holiday (Will somebody please make the Easter Bunny into a stew?), there is something especially heinous in making the birth of our Saviour about toys (Linus van Pelt is a genius; also, I refer you back to my thoughts on the Easter Bunny).
I have decided that if/when/gah-I'm-too-young-to-think-about-this I have children, they will celebrate the Feast of Saint Nicholas on December the Sixth, not on Christmas. Christmas will be about Christ, his humility, his incarnation, and his Love.