More importantly, the Julian year was eleven+ minutes longer than a solar year. The spring solstice that was used to calculate the date for Easter was moving ever earlier and by 1582 was March 11, a ten day discrepancy with the sun. A new calendar commissioned by Pope Gregory was adopted at various times throughout the world. Spain, Portugal, France, Poland and most of Italy changed in 1582. Scotland adopted the Gregorian calendar in 1600.In England and her colonies the change did not come until 1752. The day after 2 Sep 1752 was 14 Sep 1752 because the discrepancy was by then 11 days. New Year’s Day was moved to 1 January, forever confusing the Latin meanings of September, October, November and December.
Because the English knew about the calendar used in other European countries, you may find dates in the late 17th and early 18th century in January, February or March designated like this 11 Feb 1721/2. 1721 is the Julian or old style (OS) designation and 1722 is the Gregorian or new style (NS). One source recommends always using both years for dates Jan-Mar before 1752 so 15 Feb 1654 should be transcribed as 15 Feb 1654/5.A baby born 15 Feb 1675 is not illegitimate although her parents were married 15 Apr 1675. The child was born ten months after the wedding on a date that is easier to understand if written 15 Feb 1675/6.
Remember no one was born, married or died on 4 Sep 1752 – this date did not exist.