happy as the day is long

(as) happy as the day is long

Very happy; contented. I've been happy as the day is long ever since we moved to the countryside. Johnny's in a bit of a bad mood, but just give him a new toy to play with and he'll be as happy as the day is long.
See also: happy, long

happy as the day is long

Also, happy as a lark; happy as a clam (at high tide). Extremely glad, delighted, very cheerful, as in He was happy as the day is long, or When she heard the news she was happy as a lark, or Once I got the test results I was happy as a clam at high tide. The first of these similes dates from the late 1700s. The second alludes to the lark's beautiful, seemingly very happy, song. The third, from the early 1800s, alludes to the fact that clams can only be dug at low tide and therefore are safe at high tide; it is often shortened to happy as a clam.
See also: happy, long

(as) happy as the day is ˈlong/as a ˈclam/as ˈLarry

(informal) very happy: Grandpa’s as happy as a clam helping the children to fly their kites.
See also: clam, happy, Larry, long