What year did protestants split from the Roman Catholic Church?

1517, the year when Martin Luther nailed the 95 Theses Against Indulgences on the door of the Castle Church at Wittenburg , is commonly seen as the year when the Protestant Reformation began. However, it is difficult to say precisely when an actual split occurred as there were a number of protestant groups and quite a number of negotiations occurring at this time.

Luther himself remained a Catholic for some years and originally was aiming for reform. So an actual split occurred gradually, although there were a number of key events such as the Diet of Worms in 1521, where the vote went against Luther and he was then 'kidnapped' and hidden for his own protection. Prior to this he had burned a Papal Bull on December 10, 1520, indicating the firmness of his conviction regarding his own works (the Bull had called for the burning of Luther's Works). After he came out of Wartburg Castle where he had been hidden he continued the work of church reform, particularly in worship.

There are consecutive protestant histories also going on at this time and also a little later with other Protestant groups involving such people as Zwingli and Calvin.