Towel Day is an annual celebration on the 25th of May, as a tribute to the late author St. Douglas Adams (1952-2001). On that day, fans around the universe proudly carry a towel in his honour.
Text from TowelDay.org
“Hey, you sass that hoopy Ford Prefect? There's a frood who really knows where his towel is." -- President Zaphod Beeblebrox