Instead of 12 days, only 11 were skipped, and the day of the week was repeated on successive days, because at the same time the International Date Line was moved, from following Alaska's eastern border with Canada to following its new western border, now with Russia.Usually, the mapping of new dates onto old dates with a start of year adjustment works well with little confusion for events which happened before the introduction of the Gregorian calendar.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).
For example, William III of England arrived at Brixham in England on 5 November (Julian calendar), after setting sail from the Netherlands on 11 November (Gregorian calendar), in 1688.
For example, the Battle of Agincourt is universally known to have been fought on 25 October 1415, which is Saint Crispin's Day.
But for the period between the first introduction of the Gregorian calendar on 15 October 1582 and its introduction in Britain on 14 September 1752, there can be considerable confusion between events in continental western Europe and in British domains.
In England and Wales, Ireland, and the British colonies, the change of the start of the year and the changeover from the Julian calendar occurred in 1752 under the Calendar (New Style) Act 1750. designation is particularly relevant for dates which fall between the start of the "historical year" (1 January) and the official start date, where different.
In Scotland, the legal start of the year had already been moved to 1 January (in 1600), but Scotland otherwise continued to use the Julian calendar until 1752. But the start of the Julian year was not always 1 January, and was altered at different times in different countries (see New Year's Day in the Julian calendar). This was 25 March in England, Wales and the Colonies until 1752.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.