Marcus makes clear delineation about things in his control versus things out of his control. Things out of his control are indifferents and he (his mind) can have any opinion about them that he wants. As to time, the only thing relevant to him is the present. There is nothing that can be done to change the past and we only have control over the future to the extent of our plans. But a million different things could change those plans in an instant. Therefore, we really have no control over the future either.
(see also Citadel p. 113, 131-132)