Gravy Day
In 1996 Paul Kelly wrote a ballad which he called How to Make Gravy. The song is about a man in prison writing to his brother and thinking about Xmas coming up.
Hello Dan, it's Joe here, I hope you're keeping well
It's the 21st of December, and now they're ringing the last bells
If I get good behaviour, I'll be out of here by July
Won't you kiss my kids on Christmas Day, please don't let 'em cry for me
In the course of the song it becomes clear that Joe used to make the gravy for the Xmas roast so he passes on some advice to his brother about how to do it — add flour, salt, a little red wine and a dollop of tomato sauce for sweetness and that extra tang.
This song was so popular that it became an unofficial Australian Xmas anthem and somewhere along the line the 21st of December became known as Gravy Day.