Battle of the Boyne was on 1 July but there was additional activities later.
Originally, the 12 July commemoration was that of the Battle of Aughrim,[56] symbolising Irish Protestants’ victory in the Williamite war in Ireland. At Aughrim, which took place a year after the Boyne, the Jacobite army was destroyed, deciding the war in the Williamites’ favour. The Boyne, which, in the old Julian calendar, took place on 1 July O.S., was treated as less important, third after Aughrim and the anniversary of the Irish Rebellion of 1641 on 23 October O.S.
Okay, thanks.