Magellan’s return – a paradox?

(taken from One Time Fits All: The Campaigns for Global Uniformity, I. R. Bartky, Stanford University Press, 2007)

On Wednesday, 9 July 1522, the crew of the Spanish ship Victoria found themselves once again in the latitude of Portugal’s Cape Verde Islands off the coast of Africa. The ship and its thirty exhausted and ailing sailors – survivors of Ferdinand Magellan’s fleet of five ships and 265 men – has sailed westward from Seville for the Spice Islands almost three years before and were now returning home. Anchoring near the island of Santo Antão, the vessel’s captain, Juan Sebastián del Cano, ordered thirteen of the deckhands to launch a small boat and when on land barter a portion of the Victoria’s cargo of cloves for desperately needed food and water. They were also told to find out from those living on the island the day of the week.

Both Antonio Pigafetta (the diarist) and Francisco Albo (the pilot) had kept journals throughout the arduous circumnavigation. Thus they were astonished to learn that it was Thursday on the island, for their own reckoning had it Wednesday. A bewildered Pigafetta wrote, “We could not see how we had made a mistake; for as I had always kept [the day and date] well, I had set [them] down every day without any interruption.” Albo, however, concluded, “I believe that we had made a mistake of a day.”

Sometime after the ship’s return to Seville, also one day later than the reckoning aboard the Victoria, Pigafetta learned that he and Albo had made no error in their accounts.

Why?