man-day vs working day

man-day

noun
  • One person's working time for a day, or the equivalent, used as a measure of how much work or labor is required or consumed to perform some task. 

working day

noun
  • The part of a day in which work is done; the number of hours one must work per day for a specified wage. 

  • Any of those days of a week on which work is done, officially Monday to Friday in many countries (even though many people work on weekends). 

How often have the words man-day and working day occurred in a corpus of books? (source: Google Ngram Viewer )