ad kalendas Graecas

Attributed by Suetonius in Lives of the Twelve Caesars to Caesar Augustus. The kalends (also written calends) were specific days of the Roman calendar (the first of the month), not of the Greek, and so the “Greek Kalends” would never occur.

• (Classical Latin) IPA^(key): /ad kaˈlen.daːs ˈɡrae̯.kaːs/, [äd̪ käˈɫ̪ɛn̪d̪äːs̠ ˈɡräe̯käːs̠]
• (modern Italianate Ecclesiastical) IPA^(key): /ad kaˈlen.das ˈɡre.kas/, [äd̪ käˈlɛn̪d̪äs ˈɡrɛːkäs]

ad kalendās Graecās

1. (idiomatic) never at all; never in a month of Sundays.

• → English: Greek calends (calque)
• → French: aux calendes grecques (calque)
• → Italian: alle calende greche (calque)