ad kalendas Graecas

Latin phrase
ad ka·​len·​das Grae·​cas | \ ˌäd-kä-ˈlen-däs-ˈgrī-ˌkäs How to pronounce ad kalendas Graecas (audio) \

Definition of ad kalendas Graecas

: at the Greek calends : never (since the calends is a date only on the Roman calendar)