almanac vs opus

almanac

noun
  • A handbook, typically published annually, containing information on a particular subject 

  • A book or table listing nautical, astronomical, astrological or other events for the year; sometimes, but not essentially, containing historical and statistical information. 

  • A GPS signal consisting of coarse orbit and status information for each satellite in the constellation. 

opus

noun
  • A work of music or set of works with a specified rank in an ordering of a composer's complete published works. 

  • A work, especially of art. 

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