The calendar divided the year into 365 days, plus an extra day every fourth year.The year started on 25 March, and ended on 24 March.Then astronomers discovered that there was an error of eleven minutes a day, or three days every four hundred years.
Calendar reform began in continental Europe and James VI proclaimed that Scotland should adopt the Gregorian calendar on 1 January 1600.
With the Union of the Crowns in 1603 he became James I of England but the calendar change did not take place south of the Border until 1752.
In many old English legal documents dates in the months of January, February and early March give two years, for example, 1 January 1699/1700, and this has been the cause of much confusion.
An adjustment was needed and when England adopted the Gregorian calendar in 1752 Parliament decided that the date should jump directly from 2 to 14 in September with no intervening days numbered 3 to 13.
The Old Parish Register for Inveraray and Glenaray includes a comment on the changes between the August and October 1752 marriage entries: 'NB.
Upon the third of September this year the computation of time has been changed from the Julian to the Gregorian calculation so that the third day of September is reckoned the fourteenth N. and all the dates thereafter in the register are according to the Gregorian or new style and all the former to the Julian or old style' (reference OPR 513/2, page 196).Before 1582, the Julian Calendar was used throughout the Christian world.Scots legal documents of the period sometimes reflect this double-dating probably because contemporary lawyers were used to working with both systems.Dates in some English parish registers give two years.For the Scottish Old Parish Registers, however, a date of 1 January 1700 means precisely that.The English Julian calendar and the Scottish Gregorian calendar had not taken into account the actual length of the year leading to differences with dates in other countries in Europe.