A Quo
Black's Law Dictionary · Henry Campbell Black, M.A. · 1910
Black's Law Dictionary
A term used, with the correlative ad quern, (to which,) in expressing the computation of time, and also of distance in space. Thus, dies a quo, the day from which, and dies ad quem, the day to which, a period of time is computed. So, terminus A quo, the point or limit from which, and terminus ad quem, the point or limit to which, a distance or passage in space is reckoned.