noontime vs twelve hundred hours

noontime

noun
  • Approximately noon. 

  • Noon. 

  • The time at which something peaks in some way (e.g., in vitality, in influence, in reknown) (by analogy with the waxing of the sun each day). 

twelve hundred hours

How often have the words noontime and twelve hundred hours occurred in a corpus of books? (source: Google Ngram Viewer )