La page Wikipedia ne date que de 2010, et en anglais seulement. Le premier livre « Generations » date de 1991. Dans l’ouvrage « The fourth turning », les auteurs de la théorie comparent aux quatre saisons des pays tempérés, qui se déroulement dans le même ordre, mais avec des variations légères dans le timing :
"In their book, The Fourth Turning,
however, Strauss and Howe emphasize that the precise boundaries of
generations and turnings are erratic. The generational rhythm is not
like certain simple, inorganic cycles in physics or astronomy, where time and periodicity can be predicted to the second. Instead, it resembles the complex, organic cycles
of biology, where basic intervals endure but precise timing is
difficult to predict. Strauss and Howe compare the saecular rhythm to
the four seasons, which inevitably occur in the same order, but with
slightly varying timing"