high noon vs noontime

high noon

noun
  • Exactly noon; midday (when the sun is at its highest). 

  • A time, set out in advance, at which an important decision is to be made or a nemesis is to be confronted 

  • The zenith or apex of one's life or of a certain activity or era. 

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). 

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