Time immemorial (Latin: Ab immemorabili) is a phrase meaning time extending beyond the reach of memory, record, or tradition, indefinitely ancient, "ancient beyond memory or record". In law, it means that a property or benefit has been enjoyed for so long that its owner does not have to prove how they came to own it.

Is it from or since time immemorial?

If you say that something has been happening since time immemorial or from time immemorial, you are emphasizing that it has been happening for many centuries.

What does the phrase from time immemorial mean?

1 : time so long past as to be indefinite in history or tradition. — called also time out of mind.