The study of the apparent positions of celestial objects is used in astrology, a variety of divinatory practises that have been acknowledged as pseudoscientific since the 18th century. They assert to be able to reveal information about human affairs and terrestrial happenings. Since at least the second millennium BCE, various societies have practised various forms of astrology, which have their roots in calendrical systems that were used to forecast seasonal changes and interpret celestial cycles as signals of divine communications.