If you spot someone holding up a towel at work tomorrow, twisting it to form animal shapes or raising it high in an apparent bid to hitch a ride on a spacecraft, don't panic!
Relax, for it is Towel Day.
In the age of calendar odes - with days dedicated to mothers, fathers, friends, doctors and even groundhogs - May 25 is for diehard fans of Douglas Adams, the author of the hugely popular 'The Hitchhiker's Guide to the Galaxy'.
And they pay homage on this day to the science fiction writer who underlined the all-important role of a towel in the first book of the five-part series.
Towel Day was first celebrated on May 25, 2001, two weeks after the death of Adams at the age of 49, when a group of fans decided to honour his memory by celebrating the humble - yet most essential - piece of cloth.
Since then, Towel Day has become an annual tradition for his fans around the world. In India, too, Towel Day is slowly gathering ground.
A Mumbai-based lounge Bartales is hosting an interactive session on May 25, inviting people to wear a towel like a cape and share stories about the day they stood up for a cause like a 'super hero'.
"The fiction series revolves around Earth's impending doom. Today we see it nearing, with the prevalence of proxy wars, communal violence and violence against women," a spokesperson from Bartales told.
According to Bartales, compassion and standing up for other human beings is answer to the ultimate question of Life, the Universe and Everything - a recurring theme in the Hitchhiker series.
Across the world, the day is marked with pictures posted by people of their towels with a #TowelDay hashtag on social media. Some rabid fans go to work with their towels, host parties and serve drinks described in the Hitchhiker series.
This year a number of pubs across Europe have promised to offer free drinks to those who appear with towels on May 25. Some host screenings of The Hitchhiker's Guide to the Galaxy TV series.
The idea of paying tribute to the author with towels stems from a section where Adams explains its importance to interstellar travellers.
"A towel has immense psychological value. For some reason, if a strag (strag: non-hitchhiker) discovers that a hitchhiker has his towel with him, he will automatically assume that he is also in possession of a toothbrush, face flannel, soap, tin of biscuits, flask, compass, map, ball of string, gnat spray, wet weather gear, space suit etc., etc...
"What the strag will think is that any man who can hitch the length and breadth of the galaxy, rough it, slum it, struggle against terrible odds, win through, and still know where his towel is, is clearly a man to be reckoned with," he wrote.
Fans celebrate the day in ways almost as imaginative as the work of Adams.
In 2015, European Space Agency (ESA) astronaut Samantha Cristoforetti marked the day aboard the International Space Station.
In addition to recording a video where she read out from the series, Cristoforetti tweeted pictures of herself and other ISS astronauts with their towels.
Numerous pubs and cafes in the US, Brazil and other countries offer to serve the Pan Galactic Gargle Blasters and Janx Spirit - drinks that Adams held up as among the many favourites across the galaxy.
Libraries and bookstores organise group readings of excerpts from the books. A fan-run website 'towelday.org' hosts a list of events organised worldwide.
The Hitchhiker's Guide to the Galaxy started off as a radio series in 1978. Following its popularity, the series was adapted into novels and TV series.
It begins by describing an ordinary day in the very mundane life of Arthur Dent. Things escalate quickly, with his house being bulldozed to make way for a bypass, and then, within minutes, the Earth being destroyed to make way for a hyperspace bypass.
Luckily for Arthur, he manages to hitch a ride in the very spacecraft that destroyed the Earth.
"H2G2 is one of those series that is so ridiculously absurd and stupid that it's amazing. I first read it way back in school, and it was all so fascinating and funny that it had me hooked, said Manveer Singh, a 22-year-old software development engineer in Delhi.
In a foreword dated 2002, American author Neil Gaiman wrote, "The Hitchhiker's Guide to the Galaxy sequence used the tropes of science fiction to talk about things that concerned Douglas, the world he observed, his thoughts on Life, the Universe, and Everything."
"His death surprised us all, and left a huge Douglas Adams-sized hole in the world," wrote Gaiman, the author of "Don't Panic: The Official Hitchhiker's Guide to the Galaxy Companion".
