ad kalendas Graecas

[ ahd kah-len-dahs grahy-kahs; English ad kuh-len-duh s gree-kuh s ]
/ ɑd kɑˈlɛn dɑs ˈgraɪ kɑs; English æd kəˈlɛn dəs ˈgri kəs /

adverb Latin.

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

Origin of ad kalendas Graecas

literally, at the Greek calends