In researching older dates when compiling your genealogy, you may come upon years written as 1700-01 or 1700/01. You should understand what they mean and why they are used. The concepts to learn are Old Style and New Style, when the beginning of the year was determined.
In the Old Style, the beginning of the year was March 25. In 1563, France adopted January 1 as the start of the year. Scotland followed that in 1600. But, it was not until 1752 that England adopted this same practice.
Before 1752, when the year began March 25, in the records of the colonies that followed the English customs, dates between January 1 and March 24 were often indicated by 2 consecutive years, for example, 1700/01. This needed to be interpreted by the reader as to whether the Old Style or New Style was being used. If considering the New Style, February 15 would be the new year 1701. Under the Old Style, the new year had not arrived yet, and the year should be 1700.
Hyphenated double dates, for example 1700-01, mean that the specific year is not definitively known.