Post date: May 29, 2013 9:03:30 PM
Heard about it for the first time today on this blog. And found interesting... waiting for something to happen but with uncertainty or not knowing when it will happen or even if it will happen or not ! :)
It means "at some indeterminate time, and possibly never".
Searched more and found this - A french proverb, meaning "At an uncertain date", referring to the practice of the french kings of the XIIIth and XIVth centuries, of borrowing money to be returned "à Pâques ou à la Trinité", which promise was seldom regarded.