Idiom: As Happy as the Day is long Posted on 20th December 201822nd November 2018 by DoubleClick As Happy as the Day is long: Extremely content, as happy as the day is long Example: We have been happy as the day is long ever since we moved in to the UK. Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window) Related Posted in Idiom and tagged idiom A.