Keith Richards' Life is an epic account of the heyday of rock 'n' roll.
In an era when government oversight was almost nonexistent and laissez-faire capitalism was in its heyday, Kennedy excelled.
In its heyday, the miracle of AMC was always greater than the sum of its parts.
late 16c., alteration of heyda (1520s), exclamation of playfulness or surprise, something like Modern English hurrah, apparently an extended form of Middle Elish interjection hey or hei (see hey). Modern sense of "stage of greatest vigor" first recorded 1751, which altered the spelling on model of day, with which this word apparently has no etymological connection.