The problem here is that countries over Europe all took the decision to change from Julian to Gregorian at different times. Therefore , if researching for ancestors anywhere in Europe, it is worth noting when these changes took place.
There is an amazing difference 170 years from when the first countries changed to Gregorian and when England finally took on the Gregorian calendar. The difference between the two calendars was ten days, but by the time England went on board it was eleven. The change took place for the United Kingdom ( and all its colonies) on Wednesday the second of September 1751 and the next day became Thursday the 14th of September. The year used to begin officially on March th 25th ( the civil year), until then. To add to the confusion, previous to this, for some time people considered the new year's day to be January the first, yet officially, the year started on March the 25th (known as Lady Day or Annunciation Day). So sometimes the dates would be written ; JANUARY 3 1720 / 1.Giving both interpretations. Plus, the year of 1751 began in march the 25th and ended on December the 31st, as short year, and the new year ( and subsequent years) began January the first 1752 to December the 31st.
Looking at early documents you will find both dates sometimes written , and so when documenting your family history it is best to transcribe the document as you see it. Even more misleading is some documents written after 1852 when mentioning dates for pre 1852 they give both dating styles, so you could be forgiven in thinking the date wasn't really known properly and it was an estimate, whereas in fact it is using both old and new style dates for instance; January 20th 1743/4. It is worth noting that the IGI can be wrong if the dates aren't interpreted correctly.
Other Types of Dating Found in Old Documents
Widely used, especially on wills, a date would be portrayed not by calendar date but by Rengal Years. This was the length of time a reigning monarch had been on the throne. It started on the day the King or Queen came to the throne. Another type of dating is by using religious feasts and saints days. For example, the Friday before the feast of St Swithins, or so many days before or after Easter etc.
Legal systems used a different dating criteria based on recurring cycles in the agricultural and religious years. When looking at legal documents, you will come across the terms Michelmas,Hilary,Easter and Trinity, in this order; they go from October the 6th with the start of Michelmas onwards.This comes about form the court sessions that were held quarterly.