Before 1752, the new calendar in England started on 25 March.
When New Year was established as starting on 1 January, the terms Old Style and New Style came into use when quoting dates.
So, 15 February 1715 (Old Style) would be quoted as 15 February 1716 (New Style). When the day fell after 24 March, the year was the same.
In some datasets, records before 1752, and days before 25 March, give the year in both Old and New Style, eg. 23 January 1741/2 (where 1741 is Old Style and 1742 is New Style).
In the narrative of my family history, both dates will be indicated thus: 15th January 1736/7. The dates shown do not indicate any doubt about the dates; they merely refer to Old Style and New Style dates!