crack of dawn vs sunset

crack of dawn

noun
  • The first moment of daylight; before sunrise. 

sunset

noun
  • The changes in color of the sky before and after sunset. 

  • The moment each evening when the sun disappears below the western horizon. 

  • A set termination date. 

  • The final period of the life of a person or thing. 

  • The region where the sun sets; the west. 

verb
  • To phase out. 

How often have the words crack of dawn and sunset occurred in a corpus of books? (source: Google Ngram Viewer )