It all came about because a New York journalist enquired whether there was such a thing as a “Tolkien Reading Day”.

My grandparents were fishing folk from Buckie in the north of Scotland, carriers of the old stories and legends, and the trilogy has filled a certain hole in my life. I have many friends here in New York who were equally moved by the book, reignited by the film, and we all wondered: is there any day devoted informally to readings from the trilogy, in the way that “bloomsday” is devoted to Joyce?
That enquiry was sent to the Tolkien Society in January 2002. The then committee liked the idea and after a certain amount of discussion picked March 25th as “Tolkien Reading Day”. The rest, as they say, is history!
http://www.tolkiensociety.org/ed/tolkienreadingday.html