1521 (MDXXI) was a common year starting on Tuesday (link will display the full calendar) of the Julian calendar, the 1521st year of the Common Era (CE) and Anno Domini (AD) designations, the 521st year of the 2nd millennium, the 21st year of the 16th century, and the 2nd year of the 1520s decade. Events January–June January 3 – Pope Leo X excommunicates Martin Luther, in the papal bull Decet Romanum Pontificem. January 22 – Charles V, Holy Roman Emperor, opens the Diet of Worms in Worms, Germany. January 27 – Suleiman the Magnificent suppresses a revolt by the ruler of Damascus. February 2 – The Nydala Abbey Bloodbath takes place at Nydala Abbey, Sweden; the abbot and many monks are murdered by Danes. March 6 Ferdinand Magellan makes first European contact with Guam. Martin Luther is summoned to appear before the Diet of Worms. March 16 – Ferdinand Magellan reaches the Philippines. March 31 – The First Mass in the Philippines is held. April – The Battle of Tunmen occurs, in Tuen Mun (present-day Hong Kong), where the Ming Dynasty navy defeats the Portuguese navy. Arguably the first Sino-European battle in world history. April 7 Ferdinand Magellan arrives at Cebu. Martin Luther preaches an inflammatory sermon to students at Erfurt, while on his way to Worms. April 16–18 – Martin Luther is examined before Emperor Charles V and the Diet of Worms, where he proclaims, "Here I stand", regarding his belief in the Bible alone, as the standard of Christian doctrine. April 24 – Revolt of the Comuneros – Battle of Villalar: Castilian royalists defeat the rebels and execute their three leaders. April 26 – Martin Luther leaves Worms and disappears for a year – he is rumored to be murdered, but is actually in hiding at the Wartburg castle. April 27 – Battle of Mactan: Ferdinand Magellan is killed in the Philippines. May – The Italian War of 1521–26 breaks out between Charles V, Holy Roman Emperor, and Francis I of France. May 17 – Edward Stafford, 3rd Duke of Buckingham, is executed for treason in London. May 20 – Battle of Pampeluna: Allied French-Navarrese forces defeat the Spanish. May 25 – The Diet of Worms ends when Charles V, Holy Roman Emperor issues the Edict of Worms, declaring Martin Luther an outlaw. May 27 – Jiajing Emperor ascends the throne of the Ming Dynasty. June 25 –