Read this: The first European to discover Guam was Portuguese navigator Ferdinand Magellan, sailing for the King of Spain, when he sighted the island on March 6, 1521 during his fleet's circumnavigation of the globe.:41–42 When Magellan arrived on Guam, he was greeted by hundreds of small outrigger canoes that appeared to be flying over the water, due to their considerable speed. These outrigger canoes were called Proas, and resulted in Magellan naming Guam Islas de las Velas Latinas ("Islands of the Lateen sails"). Antonio Pigafetta, one of Magellan's original 18 the name "Island of Sails", but he also writes that the inhabitants "entered the ships and stole whatever they could lay their hands on", including "the small boat that was fastened to the poop of the flagship.":129 "Those people are poor, but ingenious and very thievish, on account of which we called those three islands Islas de los Ladrones ("Islands of thieves").":131

On what date did Portuguese navigator Ferdinand Magellan begin his trip around the world?
What is the answer? (If it cannot be answered, return "unanswerable")
unanswerable