hey·day /ˈheˌde/
  Hey·day interj.  An expression of frolic and exultation, and sometimes of wonder.
  Hey·day n.  The time of triumph and exultation; hence, joy, high spirits, frolicsomeness; wildness.
     The heyday in the blood is tame.   --Shak.
     In the heyday of their victories.   --J. H. Newman.
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  heyday
       n : the period of greatest prosperity or productivity [syn: flower,
            prime, peak, bloom, blossom, efflorescence, flush]