merry as the day is long
merry as the day is long
old-fashioned Jubilant; especially carefree, lively, and full of fun. Tom is playing outside, merry as the day is long. Though he acts as merry as the day is long, he is dreadfully unhappy when he is all alone.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.