Full Idea
For Descartes, Hobbes and Spinoza, if a state of things is possible, it must occur at some time, whether past, present or future. For Leibniz possibility makes no reference to time; an individual is possible if its concept contains no contradiction.
Gist of Idea
Early modern possibility is what occurs sometime; for Leibniz, it is what is not contradictory
Source
Richard T.W. Arthur (Leibniz [2014], 4 'Contingent')
Book Reference
Arthur, Richard T.W.: 'Leibniz' [Polity 2014], p.92
A Reaction
It has always struck me as fallacious to say that anything that is possible must at some time occur. If '6' is possible on the die, what will constrain it to eventually come up when thrown? Mere non-contradiction doesn't imply possibility either.