The second law of thermodynamics is about systems that are well described by a small set of macroscopic variables. The evolution of an initial macrostate prepar

The second law of thermodynamics is about systems that are well described by a small set of macroscopic variables. The evolution of an initial macrostate prepared by an experimenter who can control only the macrovariables is reproducible. When a thermodynamical system is prepared in such a reproducible way the preparation is happening in the past, by definition. The second law is about how part of the information that we had about a system - constrained to be in a macrostate - is “lost” when we “forget” the previous state and describe it using just the current macrostate. We know more precisely the past than the future - the previous state is in the past by definition.