ceremony vs red letter day

ceremony

noun
  • A ritual, with religious or cultural significance. 

  • An official gathering to celebrate, commemorate, or otherwise mark some event. 

  • A formal socially established behaviour, often in relation to people of different ranks; formality. 

  • Show of magnificence, display, ostentation. 

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 ceremony and red letter day occurred in a corpus of books? (source: Google Ngram Viewer )