'Calendar' (ii) was a British naval undertaking to sweep the West Scheldt branch of the Scheldt river estuary and so remove German mines during operations to open and then keep open the port of Antwerp to Allied shipping bringing in supplies and equipment to support the eastward movement of Field Marshal Sir Bernard Montgomery’s Allied 21^st Army Group and Lieutenant General Omar N. Bradley’s US 12^th Army Group (November 1944/January 1945).