The sun has long been a potent symbol of worldly power, mythological cosmology, Christian revelation, and philosophical enlightenment. To conjure with it musically is to open a vast field of the associative possibilities of illumination and its others: figures of emergence, ascension, power, fatal strength, attenuation, obscurity. In his symphonic trilogy on the times of the day—nos. 6 (Le matin), 7 (Le midi), and 8 (Le soir)—Haydn traces the diurnal movement of the sun across all three works in ways that reveal a sophisticated understanding of the sun's many cultural resonances. This opus constitutes, in effect, Haydn's debut at the Esterházy court in 1761, a year in which the Transit of Venus across the sun attracted local and global fascination and intense astronomic study. Beyond demonstrating his cultural range to the court, Haydn's focus on the sun's trajectory also helps to explain many of the puzzling musical features of the trilogy, especially the unusual slow movements. These works cast new light on Haydn's return to musical settings of the diurnal cycle at the dusk of his career, in The Creation (1798) and The Seasons (1801), and reflect the Enlightenment composer's engagement with multiple fields of knowledge and experience.