 The Jyotisha text "Brahma-siddhanta", probably composed in the 5th century CE, discusses how to use the movement of planets, sun and moon to keep time and calendar.This text also lists trigonometry and mathematical formulae to support its theory of orbits, predict planetary positions and calculate relative mean positions of celestial nodes and apsides.The text is notable for presenting very large integers, such as 4.32 billion years as the lifetime of the current universe.