January 6th, 1854, is considered to be the birthday of Sherlock Holmes. You can read about the humorous history of this (somewhat arbitrary) celebration in this 2009 article.
I'm a firm believer in 1854 as the birth year, since Holmes is described as about sixty years old in "His Last Bow," which takes place in 1914. As for January 6th, I'm not sure about it, but I don't mind it. (For one thing, it's the same day as Epiphany, which helps me remember!)
In observation of his birthday, how about a discussion question - What is your first memory of Sherlock Holmes?
When I was about nine or ten, I discovered The Original Illustrated Sherlock Holmes on my family's bookshelf. It wasn't the complete stories, but about 2/3 of them, with the illustrations by Sidney Paget. The first one was "A Scandal in Bohemia," and while I couldn't have told you the definition of some words - like "blackmail" - I was absolutely carried away by the story, and of course, by Holmes and Watson.
Enthralled, I devoured the entire book in a very short time. Like Watson, I was floored by Holmes's deductions. Unusual for me at the time, I got emotional over some plots - "The Greek Interpreter" terrified me, and I was heartbroken by "The Final Problem." I was completely immersed in the series.
As I got older, Sherlock Holmes the character influenced my life in a lot of ways, which maybe I will talk about in another post. Suffice it to say, though I've experienced many books, I'm not sure if any have affected me as much as the Sherlock Holmes series.