Alexandra Harris, author of Romantic Moderns and winner of the Guardian First Book Award, considers how we pass, measure and mark time, and ultimately, what it means to us.

Robinson Crusoe, stuck on his island, had no need to keep time with the world. Certainly he had no boats to catch or appointments to keep. And yet he made it a priority to keep track of the passing days. In mid-October 1659, the thought struck him: ‘It came into my mind that I should lose my reckoning of time’. To avert that disaster he put up a large post on the beach and cut a notch in it each day – doggedly, faithfully, year after year. He had sole responsibility for this makeshift calendar and no way of checking it against an external measure, so he faced a problem when he woke up one afternoon having slept, drunkenly, for a very long time. How long? Could he have slept through a whole day? In which case his calendar would forever be wrong and there was just no way of telling…