Australia Day at Melbourne Park was seniors day, USA day, a day for power tennis, schmaltzy day, but most of all Williams day, incorporated.
Serena beat the improbably resurrected Mirjana Lucic-Baroni, Venus beat CoCo Vandeweghe, who is still on her first coming, both sisters by playing in the character they pioneered in womens tennis, hitting off the court opponents who tried to hit them off the court. If there was slice or a drop shot in either match, in must have been in an ad break.
So the Williams sisters meet again in a major final, for the ninth time, but the first time for nearly 10 years and the first time at the Australian Open since 2003. Australia Day became the day that was once everyday, but seemed destined never to dawn again.
Everything old was new again, not least the dialogue. "A total inspiration, my big sister," said Serena. "She's basically my life and my world. I just feel like no matter what happens, we've won," said Serena. Her syntax was unarguable; either she will have her 23rd major, or Venus her eighth. In the Williams household, straight to the pool room means straight to the room where the trophies are pooled.
Graciously, each sister's first thought was not for the other, but for her gallant opponent. Lucic-Baroni's return from purgatory was the feel-good story of the women's tournament, and she knew it. Before exiting, she took a selfie of herself and the crowd. "She's such inspiration," Serena said. "I was so honoured to play her today." Rivals, Venus included, have to learn to stop inspiring Serena; it leads only to their expiry.
Really, January 26 was everyone's day except Australia's. In the men's semis, there were two sentimental favourites and two logical, but in the women's, there were favourites of every kind: the overwhelming, the romantic, the mushy and that most Australian kind, the underdog.
Three super-veterans and one super-punk. Three Americans and an American resident (but a loser, from somewhere over there: wait until the president hears). Two with one name, one with two, and CoCo. Families of all sorts: the dynastic, the divided, the dysfunctional, and in tennis terms, the "family", a kind of mafia.
Two on improbable comeback trails, one still coming along and one who never goes away. Two whose time had gone, one whose time was still to arrive, one who is timeless. The forgotten, the one who likes not to be forgotten and the unforgettable: pick the eyes out of that. This was the day's business.
Somehow, even the losers would win something this day; everyone would take home at least a door prize. For Vandeweghe, it was invaluable experience; she had never been to the second week of a major before, let alone a semi-final. For Lucic-Baroni, it is an implausibly exciting immediate future; after all, she was the second youngest of these four semi-finalists.
Venus went first. Her match was a torrid affair. Top spin was a Trump presser, slice a piece of Mom's apple pie: neither was seen or heard here. For two-and-a-half hours, they crunched the ball at one another.
But the biggest crunch was Venus' serve; Vandeweghe would only get through it once in 13 opportunities, in the second game of the match. Venus hit 11 aces; her tournament aggregate until then was seven.
Vandeweghe peaked in the first set tie-breaker, winning six of the last seven points to seize it. But she thought then that her opponent would pop off for a nanna nap, she was rudely disabused. A run of 10 points in a row early in the second set established Venus in the ascendancy, and she would not again fall behind.
But she was not merely patronising Vandeweghe when she said at match's end: "It means so much, mostly because she played so well. I had to play the whole time, There was never a moment of relaxation, ever."
Now there was, though, and two dozen pirouettes followed, and much hollering, ecstasy personified. Off camera, she said that although her game had grown and re-grown, she was still her juvenile self - at 36. "Everyone has their moment in the sun. Maybe mine has gone on for a while," she said, "but let's keep it going. I've got nothing else to do."
Serena did not see any of Venus's win; she was limbering up. Venus did not see any of Serena's win; she was still warming down. It lasted the bare 50 minutes, predictably enough.
Lucic-Baroni was not disgraced. She is from another time, but not another way. However hard Serena hit the ball, she walloped it just as hard. Of course, there was also the not inconsiderable matter of landing it in court. Serena's entire winning tally was made up of her unreturned serves and Lucic-Baroni's errors, so-called.
But it was a brave way to play, and like Mischa Zverev against Roger Federer three nights previously, the only way for her. This pair had not met since a brace of matches in 1998 - last century! - but you imagine that they did not play so differently then.
Both were rising teenage stars, both with family problems, you might say. Lucic-Baroni's have been well, if obliquely documented. Serena's was to win boasting rights in her own house. Nineteen years later, it still is.