Well, speaking on behalf of the world today, thanks!
The reader was duly warned by the cover: no rockets. Mythological stuff. Sprites. Magic. All that hoo-hah nonsense full of laments for Times Gone By, when the glades echoed with the pipes of Pan, and so on.
For a while there were lots of "Day of The" things. It was appended to things to make them sound more momentous. Its time has come! You didn't think what it would be like the day after the day of the minotaur or dolphin or whatever. Probably lots of cleaning up.
Not used much anymore.