festivity vs red letter day

festivity

noun
  • A festival or similar celebration. 

  • An experience or expression of celebratory feeling, merriment, gaiety. 

red letter day

noun
  • A particularly significant day; a day of personal or sectarian celebration. 

  • A day marked in red on calendars; a church feast day. 

How often have the words festivity and red letter day occurred in a corpus of books? (source: Google Ngram Viewer )