expiry date vs leave-taking

expiry date

noun
  • The date on which something runs out or expires and becomes out of date, in many cases needing renewal. 

leave-taking

noun
  • The act or process of taking leave (time away from work) 

  • The process of saying goodbye. 

How often have the words expiry date and leave-taking occurred in a corpus of books? (source: Google Ngram Viewer )