mañana vs one day

mañana

adv
  • Some unspecified time in the future. 

  • Tomorrow. 

one day

adv
  • At some unspecified time in the future. 

  • Used other than figuratively or idiomatically: see one, day. 

  • At some unspecified time in the past. 

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