Dictionary.com
Thesaurus.com

ad kalendas Graecas

American  
[ahd kah-len-dahs grahy-kahs, ad kuh-len-duhs gree-kuhs] / ɑd kɑˈlɛn dɑs ˈgraɪ kɑs, æd kəˈlɛn dəs ˈgri kəs /

adverb

Latin.

  1. at no time; never: from the fact that the Greeks did not reckon dates by calends.

Etymology

Origin of ad kalendas Graecas

Literally, “at the Greek calends”

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.