The days had folded one into another and mixed so that after two or three weeks he only knew time had passed in days because he made a mark for each day in stone near the door to his shelter. Real time he measured in events. A day was nothing, not a thing to remember—it was just sun coming up, sun going down, some light in the middle. But events—events were burned into his memory and so he used them to remember time, to know and to remember what had happened, to keep a mental journal.
