It's not exactly a national holiday - yet - but "gravy day" is being well celebrated in Australia, thanks to a song and plenty of internet jokes.
What is gravy day? It began with a 1996 song called How To Make Gravy by popular Australian singer Paul Kelly.
Its lyrics tell a fictional tale of a man in jail writing to his family about longing to be with them at Christmas.
That letter is penned on 21 December - a date that, in real life, has been deemed increasingly worth celebrating.
And many Australians did on Friday, especially on social media.
Merry Gravy Day to all who celebrate!— Gina Rushton (@ginarush) December 20, 2018
"GravyDay", "Paul Kelly" and "the 21st of December" were trending terms on Twitter, with many posts playing off How To Make Gravy's narrative.
Joe, the song's made-up protagonist, sings about his family's traditions, such as relatives "driving down from Queensland" and "flying in from the coast".
The song has even been likened to "an Australian Christmas carol". Instead of northern-hemisphere references to cold things, Joe anticipates a hot Christmas Day.
"They say it's gonna be a hundred degrees, even more maybe," the lyrics read, "but that won't stop the roast".
His emotional messages to family - such as "give my love to Angus and Frank and Dolly" - have become a particular focus of fun.
Radio stations also picked up on the celebrations.
Spare a thought for all the poor ABC local radio presenters today getting bombarded with requests for 'the gravy song' #gravyday— Angus Randall (@angusrandall) December 20, 2018
And just what is the best gravy recipe? According to the lyrics, it is: "Just add flour, salt, a little red wine, and don't forget a dollop of tomato sauce, for sweetness and that extra tang."
Some said they would follow that advice, but others questioned the recipe.
It’s a beautiful song but i will never add a dollop of tomato sauce to any gravy I make that is ridiculous— F Onthemoon (@firstdogonmoon) December 20, 2018
Kelly himself tweeted "Happy Gravy Day" on Friday.
"You never know what's going to happen to the song after you write them," he told the Australian Broadcasting Corporation last year.