Magellan's voyage and Pigafetta's "riddle"?

Question

For three years Magellan and his flotilla of ships circumnavigated the globe.On Tuesday, Sept. 1519 their journey started at Sanlucar de Barrameda, a port city on the Atlantic coast of Spain, and traveled southwest to the coast of Brazil. From there, they continued down the coast of Brazil and headed through the Strait of Magellan (right above Cape Horn), and west through the Pacific. They reached the Pilippine Islands. After sailing southeast away from the Philippines, the remainder of the crew finally arrived at the Spice Islands (known today as the Moluccas) and took a load of cloves. Then they ventured west through the Indian Ocean, through the Cape of Good Hope, and north, where they docked at Sanlucar de Barrameda, their place of departure, on Saturday, Sept. 6, 1522. Yet the Spaniards insisted that is was the 7th. How could this be? Antonio Pigafetta, a venetian from the ship, checked his detailed logbook that he had marked their daily positions in, and it said the 6th. How?

Answer 1

Circumnavigating the turning earth from
east to west, (same path as the sun),
they "lost" a day. The additional time was
added to the days they experienced in small
increments as they traveled.

Answer 2

ah that is so weird! we both asked the same question at the same time! i have to do a school report on it...

i have no clue and im asking all my friends. i just know it has something to do with the sun? and they lose a day by travelling against the earth's rotation or something. but how can they lose a day over three years? i have no clue..