Old Style Calendar
Before 1752 the year began on Lady Day, March 25th,. Dates between January 1st and March 24th were at the end of the year. Old Style (O.S.) and New Style (N.S.) are used to indicate whether the year has been adjusted. Often both dates are used.
Essex County, Massachusetts was created on May 10, 1643 by the General Court of the Massachusetts Bay Colony, when it ordered "that the whole plantation within this jurisdiction be divided into four sheires."
The Salem witch trials were between February, 1692 and May, 1693.