April 30, 311 Emperor Galerius legal recognition of Christians in the Roman Empire. 313 Roman emperor Licinius unified the entire Eastern Roman Empire under his rule. 1006 Supernova was observed in Europe, China, Japan, and Egypt. 1513 Edmund de la Pole, Yorkist pretender to the English throne, was executed on the orders of Henry VIII. 1527 Henry VIII of England and King Francis of France signed the treaty of Westminster.