before the present (used with a measurement of time).
Usage
When ago is followed by a clause, the clause should be introduced by that rather than since, e.g. it was sixty years ago that I left this place (not it was sixty years ago since I left this place).
Etymology
ME ago, agone, past part. of the obs. verb ago ‘pass’, used to express passage of time.
Teacher: Chris, you need to pay more attention to your attendance.
Chris: ____________ I thought students could join clubs.
Teacher: Clubs are fine, but you should also concentrate on your studies.
Chris: I know. I’ll try to manage my time more effectively.