The Hitchhiker's Guide To The Galaxy. Douglas Adams, the author, died five years and fourteen days ago. The 25th of May was chosen to be the "Towel Day". Towels are an important item in the book(s). People who want to pay tribute to the great author (and outspoken Mac fan, featured on Apple's site several times, too...) have a towel with them on this day of the year. Mine's a blue.