happy as the day is long . happy as the day is long {adj. phr.} Cheerful and happy. Carl is happy as the day is long because school is over for the summer. Categories: add yours {adj. phr.} Source: A Dictionary of American Idioms by A. Makkai, M.T. Boatner, J.E. Gates © 2025 To section: H Subscribe to: American IdiomsIdioms feedEnglish languageHome page and general feed Add my comment