foretime vs one day

foretime

adv

  • In former times. 

noun

  • A time previous to the present, or to a time alluded to or implied; former time or times. 

one day

adv

  • At some unspecified time in the past. 

  • At some unspecified time in the future. 

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

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