dateless vs unflagging

dateless

adj
  • Timeless; immortal 

  • Without a date imprinted, assigned, or associated. 

  • Out of one's head; deranged. 

  • Thick-headed. 

  • Having no date—a meeting with a lover or potential lover. 

  • Without a start; immemorial 

unflagging

adj
  • Never tiring or lacking energy; without rest; without slowing. 

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