Time: And time again

The concept of time as it appears in quantum, classical, and statistical physics is revisited. By combining special relativity and time-independent quantum field theory, we obtain the time-dependent Schrödinger equation, but time, t, and position, r, are regarded as parameters, not operators. When examined from another point of view, an argument based on the photon wave function is developed in order to show that the time in quantum mechanics is the same as the time in Maxwellʹs equations. Finally, the issue of time is again addressed, but this time from the perspective of statistical time, i.e., time as derived from thermodynamics.