May Revolution
The mutiny of Aranjuez in 1808 led King Charles IV of Spain to abdicate in favor of his son, Ferdinand VII. Charles IV requested that Napoleon restore him to the throne; instead, Napoleon crowned his own brother, Joseph Bonaparte, as the new Spanish King. These events are known as the Abdications of Bayonne. Joseph's coronation was met with severe resistance in Spain, which started the Peninsular War, and the Supreme Central Junta took power in the name of the absent king. This also led to Spain switching allegiances from France to Britain. France eventually invaded Sevilla, and a Council of Regency based in Cadiz replaced the disbanded Supreme Central Junta.
Sun of May
The specification ""of May"" is a reference to the May Revolution which took place in the week from 18 to 25 May 1810, which marked the beginning of the independence from the Spanish Empire for the countries that were then part of the Viceroyalty of the Río de la Plata. A legend claims that as the new government was proclaimed, the sun broke through the clouds, which was seen as a good omen.