May 1

The Roman emperors Diocletian and Maximian jointly abdicated on the same day, Diocletian at Nicomedia and Maximian at Milan, in the first voluntary imperial abdication.

Arcadius, Eastern Roman emperor since 383, died of natural causes in Constantinople, leaving the throne to his young son Theodosius II.

Swami Vivekananda gathered the monastic and lay disciples of Ramakrishna at Balaram Bose's Kolkata house and founded the Ramakrishna Mission.

The Iranian Shia scholar and philosopher Morteza Motahhari, a prolific writer on Islamic thought, was killed in Tehran.

Santiago Ramón y Cajal was born in Petilla de Aragón, Spain. His finely detailed drawings of nerve cells showed the brain is built from individual neurons, work honored with the 1906 Nobel Prize.