The official change of the seasons. I’ll oblige with some appropriate versification from the Middle Ages–in the original Middle English. (The modern translation is a touch … earthier than expected!)

Sumer is icumen in,
Loude sing cuckou!
Groweth seed and bloweth meed,
And springeth the wode now.
Sing cuckou!

Ewe bleteth after lamb,
Loweth after calve cow,
Bulloc sterteth, bucke verteth,
Merye sing cuckou!
Cuckou, cuckou,
Wel singest thou cuckou:
Ne swik thou never now!