by the time vs whenever

by the time

conj

  • When (some future event has come to pass). 

whenever

conj

  • When. 

  • Every time that. 

  • At any time that. 

  • Regardless of the time that. 

  • At the (single) time that, no matter when. 

adv

  • When ever: emphatic form of when. 

  • At any time. 

How often have the words by the time and whenever occurred in a corpus of books? (source: Google Ngram Viewer )