Hawking (1988: 147):
Our subjective sense of the direction of time, the psychological arrow of time, is therefore determined within our brain by the thermodynamic arrow of time. Just like a computer, we must remember things in the order in which entropy increases. This makes the second law of thermodynamics almost trivial. Disorder increases with time because we measure time in the direction in which disorder increases.
From the perspective of Systemic Functional Linguistic Theory, the psychological arrow of time is the direction of the unfolding of processes of consciousness, such as construing experience as meaning, and (re)construing meaning as the second law of thermodynamics.
Time measures the unfolding of processes, whether the processes result in increased overall disorder or increased local order (as in self-organising systems).