12th of never
n.— «The Biplane supposedly has a V-4, but the show bike is most likely a make-believe mockup. Looks to be straight out of a video game. When will either Suzuki be produced? Right after the 12th of Never.» —“Whees: Tokyo Motor Show: Two-Wheel Thunderdome” by Jerry Garrett New York Times Oct. 29, 2007. (source: Double-Tongued Dictionary)
Further reading
In 1916, a small-town newspaper in Pennsylvania printed a fanciful item about a local gathering with a guest list that included, among others, Miss Ella Vader, Mr. Ray Zor, and other punny names. This is part of a complete episode. Transcript of...
A woman whose husband speaks Guaraní, Spanish, German, English, Italian, plus a bit of liturgical Hebrew, notices a curious thing happening while he was taking notes during lessons with a rabbi. As he jotted notes in Spanish and Guaraní, he used his...
It’s from an old folk song, variously known as “I Gave My Love a Cherry” or “The Riddle Song”: http://lyricsplayground.com/alpha/songs/numbers/12thofnever.shtml
Oops! Allow me to correct myself. Although the tune is quite old, the song “The Twelfth of Never” (containing, obviously, the phrase) is credited to Jerry Livingston and Paul Francis Webster, and was recorded by Johnny Mathis in 1957.