Passage: Early next morning, 20 May, seeing Husvik Harbour below them, they knew that they were on the right path. At seven o'clock in the morning, they heard the steam whistle sound from Stromness, "the first sound created by an outside human agency that had come to our ears since we left Stromness Bay in December 1914". After a difficult descent, which involved passage down through a freezing waterfall, they at last reached safety. Shackleton wrote afterwards: "I have no doubt that Providence guided us ... I know that during that long and racking march of 36 hours over the unnamed mountains and glaciers it seemed to me often that we were four, not three". This image of a fourth traveller—echoed in the accounts of Worsley and Crean—was taken up by T. S. Eliot in his poem The Waste Land.

Question: What was the date when they saw Husvik Harbour?
20 May