The year that marked the beginning of the Reformation in Christianity is 1517, when Martin Luther famously posted his Ninety-Five Theses. This act challenged the practices of the Catholic Church, particularly the sale of indulgences, and called for reforms. Luther's ideas sparked widespread debate and led to the emergence of various Protestant denominations. The Reformation significantly impacted European society by promoting individual interpretation of the Bible, questioning clerical authority, and leading to religious and political changes that would shape the modern Western world.