Stromboli

Avar–Byzantine wars: The Avars lift the siege at the Byzantine stronghold of Tomis. Their leader Bayan I retreats north of the Danube River after the Avaro-Slavic army is decimated by the plague.

The people of Sicily rebel against the Angevin king Charles I, in what becomes known as the Sicilian Vespers.[1]

Edward I sacks Berwick-upon-Tweed, during armed conflict between Scotland and England.[2]

Guru Gobind Singh establishes the Khalsa in Anandpur Sahib, Punjab.[3]

Joachim Murat issues the Rimini Proclamation, among the earliest calls for Italian unification.[4][5]

Physicist Augustin Fresnel reads a memoir on optical rotation to the French Academy of Sciences, reporting that when polarized light is "depolarized" by a Fresnel rhomb, its properties are preserved in any subsequent passage through an optically-rotating crystal or liquid.<span class="mw-reflink-tex...