1582-1701 – A Very Important Period

Carolyn L. Barkley writes on GenealogyandFamilyHistory.com in her article 1752 – A Very Important Date about the introduction of the Gregorian calendar. England and its colonies introduced the calendar rather late, in 1752. The former New Netherland colony, however, had already used the new calendar since the beginning of the Dutch settlement:

"Dutch settlers along the Hudson River in New York and northern New Jersey were already using the Gregorian calendar when they came to America. After 1660, when the English took over the Dutch settlements, the civil and church recorders in Dutch towns continued the use of the Gregorian calendar despite the British government and its use of the Julian calendar for almost an additional one hundred years."

In some parts of The Netherlands, the Gregorian calendar was introduced in 1582, shortly after the new calendar was decreed by Pope Gregory XIII. But it took a long time before the new calendar was used everywhere in the Dutch Republic. The last province to use the Gregorian calendar was Drenthe, in 1701. For well over a century, the old and the new calendar were used side by side in The Netherlands. Many documents from this era had a dual date: 9/19 October 1660. Other documents used abbreviations like O.S., S.V. (stilo vetere) or S.A. (stilo antiquo) for the old style (Julian) calendar, and N.S. or S.N. (stilo novo) for the new style (Gregorian) calendar.

The new calendar was introduced on the following dates:

• Zeeland and Brabant: 25 December 1582 followed 14 December.
• Holland: 12 January 1583 followed 1 January.
• Groningen city: 11 March 1583 followed 28 February. Groningen went back to old style in 1594: 11 November 1594 followed 20 November.
• Gelderland: 12 July 1700 followed 30 June.
• Utrecht and Overijssel: 12 December 1700 followed 30 November.
• Friesland and Groningen (city and province): 12 January 1701 followed 31 December 1700.
• Drenthe: 12 May 1701 followed 30 April.

I don't know when Limburg introduced the Gregorian calendar, but I expect this happened in the 1580s.

Before 1700 the difference between the calendars was 10 days, after 1700 11 days (1700 was a leap year in the Julian calendar but not in the Gregorian calendar).

Years commonly started on 1 January since at least the late 16th century, but there are exceptions throughout the first half of the 17th century. In these cases, the year would start at 25 March, Christmas, or Easter.