“Time immemorial” is usually used poetically today, often in travel shows. So: “men have been fishing in this small Greek village since time immemorial”.
What you might NOT know is that “time immemorial” has an actual start date: June 6, 1189.
The Statute of Westminster of 1275 was the first attempt to codify the laws of England. As part of this, the idea of “time immemorial” was introduced – a time which was declared “the extent of human memory”. The date chosen was Richard I’s accession day.
So if there was a land dispute, if a family could find witnesses to prove that their goats had been grazing on the land since June 6, 1189, then the courts found for the family. It was a kind of “statue of limitations”, if you will.