Specialists have tried to give a functional and symbolic meaning to the layout of the floor plan of the Monastery of El Escorial; However, with few exceptions, historiography has reported little or poorly on the light consequences derived from the solar direction of the building's axis, which is why, to date, it has not been possible to conclusively determine the reason for its southeastern declination. The present study takes into consideration, apart from the scientific knowledge of the time, the local liturgy, the sensory perception of the 16th century and the possible particular affects, some verifiable facts, the hitherto unpublished annual reading of the positions of the sun on the structure of the monument. The application of this methodology reaches the conclusion that the location and orientation of the king star in San Lorenzo el Real obeyed three fundamental commemorations: birth of Charles V, Transfiguration of Jesus and birth of Philip II.