red letter day vs revel

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. 

revel

noun
  • An instance of merrymaking; a celebration. 

  • A kind of dance. 

  • A wake for the dead. 

verb
  • To make merry; to have a happy, lively time. 

  • To take delight (in something). 

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