17 – Battle of Acheloos: Tsar Simeon I of Bulgaria decisively defeats a Byzantine army.
1000 – The foundation of the Hungarian state by Saint Stephen. Today celebrated as a National Day in Hungary.
1083 – Canonization of the first King of Hungary, Saint Stephen and his son Saint Emeric.
1308 – Pope Clement V
1467 – The Second Battle of Olmedo takes places as part of a succession conflict between Henry IV of Castile and his half-brother Alfonso, Prince of Asturias.
1613 – Elisabeth Sophie of Mecklenburg, German poet and composer (d. 1676)
984 – Pope John XIV
1823 – Pope Pius VII (b. 1740)
1914 – Pope Pius X (b. 1835)
Wow, August 20th is not a good day for Popes!