Historical letters dating to 1700
The Battle of the Boyne was commemorated with smaller parades on 1 July.However, the two events were combined in the late 18th century, and continue to be celebrated into modern times as "The Twelfth".Friday, 6 October 1867 was followed by Friday, 18 October.
From 1155 to 1752, the civil or legal year in England began on 25 March (Lady Day) The corresponding date in the Gregorian calendar is 9 February 1649, the date by which his contemporaries in some parts of continental Europe would have recorded his execution. During the years between the first introduction of the Gregorian calendar in continental Europe and its introduction in Britain, contemporary usage in England started to change.This maps to 11 July (Gregorian calendar), conveniently close to the Julian date of the subsequent [and more decisive] Battle of Aughrim on 12 July 1691.This latter battle was commemorated annually throughout the eighteenth century on 12 July, following the usual historical convention of commemorating events of that period within Great Britain and Ireland by mapping the Julian date directly onto the modern Gregorian calendar date (as happens for example with Guy Fawkes Night on 5 November).The consequence was that the basis for calculation of the date of Easter as decided in the fourth century had drifted from reality. In the case of Eastern Europe, for example, all of these assumptions would be incorrect.The Gregorian calendar reform also dealt with the accumulated difference between these figures, between the years 3 (1750 in the British Empire), by skipping 10 dates (11 in the case of the Ireland, Great Britain and her colonies) to restore the date of the vernal equinox to approximately March 21, the approximate date it occurred at the time of the First Council of Nicea in 325.