Comments on the Sign of CP Asymmetries

Several experiments are about to measure the CP asymmetry for $B \to \psi K_S$ and other decays. The standard model together with the Kobayashi-Maskawa ansatz for CP violation predicts the sign as well as the magnitude for this asymmetry. In this note we elucidate the physics and conventions which lead to the prediction for the sign of the asymmetry.