days of yore vs halcyon days

days of yore

noun
  • The past; bygone days. 

halcyon days

noun
  • A period of calm, usually in the past and often nostalgic. 

  • Period of calm during the winter, when storms do not occur. 

How often have the words days of yore and halcyon days occurred in a corpus of books? (source: Google Ngram Viewer )