20th century research and practice of science led to advancement in the fields of communication, engineering, travel, medicine, and war. 20th century The 20th (twentieth) century was a century that began on January 1, 1901 and ended on December 31, 2000. It was the tenth and final century of the 2nd millennium. It is distinct from the century known as the 1900s which began on January 1, 1900 and ended on December 31, 1999. The 20th century was dominated by a chain of events that heralded significant changes in world history as to redefine the era: flu pandemic, World War I and
Catholic Church in the 20th century into the 20th century, Catholics—even if no longer resorting to persecution—still defined Protestants as heretics. Thus, Hilaire Belloc - in his time one of the most conspicuous speakers for Catholicism in Britain - was outspoken about the "Protestant heresy". He also defined Islam as "A Christian heresy", on the grounds that Muslims accept many of the tenets of Christianity but deny the godhood of Jesus (see Hilaire Belloc#On Islam). In the second half of the century - and especially in the wake of Vatican II - the Catholic Church, in the spirit of ecumenism, no longer referred to Protestantism as