Ptolemy 'invents' the Equation of Time While the irregular daily movement of the sun was known to the Babylonians, Claudius Ptolemy, a Greek astronomer working in Alexandria around AD 150, is credited with 'inventing' the Equation of Time. This is because he was the first to tabulate the equations in Book III of his great astronomical work, the Almagest, a study that is primarily concerned with the sun's anomaly (Toomer 1998, 153–156). In 1672–1673, just after the establishment of the Greenwich Observatory in England, the first Astronomer Royal, John Flamsteed, published his Equation of Time tables for the conversion of apparent solar time (or sundial time) to mean clock time. Eventually, this task was mechanised by clockmakers such John Shelton the Younger, who made one of the earliest equation mechanisms. His clock, the Teiger Shelton Longcase, dated 1736 and exhibited here on Clocktime, is one of the earliest surviving examples of the equation mechanism in its final and most complicated form. Reference Toomer, G. J. 1998. Ptolemy’s Almagest. Princeton, NJ: Princeton University Press.
