One considers the spectrum of the monodromy operator of the Schrödinger operator ℏ (t) =- Δ +x (x, t) with a potential which is periodic with respect to time. It is shown that under certain conditions on the potential there is no singular continuous spectrum and one investigates the point spectrum of the monodromy operator. Under certain conditions on the potential q(x, t), periodic with respect to time, one shows the absence of the singular continuous spectrum for the monodromy operator corresponding to the Schrödinger operator - Δ+q,(x,t).