I discovered this week that “time immemorial” isn’t just philosophical or poetic, it has a legal definition. In British Statute Law, it actually had a starting point in time. In 1275, the First Statute of Westminster, decided the time beyond legal memory, time immemorial, was set as July 6, 1189. This is the date when King Richard I was crowned.

Obviously this definition has been updated and modified over time and the new definitions vary between jurisdictions and the aspect of law you are reviewing. Still an interesting bit of background to a well known phrase.