The Synod of Whitby (664 A.D.) was a Northumbrian synod where King Oswiu of Northumbria ruled that his kingdom would calculate Easter and observe the monastic tonsure according to the customs of Rome, rather than the customs practised by Irish monks at Iona and its satellite institutions. The synod was summoned at Hilda's double monastery of Streonshalh (Streanæshalch), later called Whitby Abbey.