Adventists are a group of Protestant Christians known for their belief in the imminent Second Coming of Jesus Christ. Some synonyms that can be used to refer to Adventists include Millerites, after William Miller who predicted the return of Christ in the mid 19th century, Sabbatarians, a reference to their observance of the seventh day Sabbath, and Prophecy believers, as Adventists place a heavy emphasis on studying Bible prophecies. Other phrases may include Second Coming Christians, who believe that Christ's return is imminent, and Apocalyptic faith adherents, due to their emphasis on the Book of Revelation and end-time events.