System used by the English in Early Colonial America

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The Julian Calendar which was introduced in Rome in 46 B.C. established the 12 month year of 365 days with each fourth year having 366 days and each month had 30 or 31 days except February which had 28 or, every leap year, 29 days. The problem with this calendar was that after nearly 1600 years it was no longer synchronized with the seasons.

The Gregorian Calendar was introduced in 1582 by Pope Gregory XIII to correct a slight error in the Julian calendar, but the new calendar was not adopted by Great Britain or the American colonies until approximately 1752.

When reading about colonial times, one often comes across a date designated as Old Style or simply a date such as 1675/76. I always wondered what that double date meant. I found the answer to this question quite by accident as I was reading A History of Hatfield Massachusetts by D. W. Wells and R. F. Wells. These two chroniclers were writing about a will made by a gentleman on January 29, 1659-60 and explained it as follows. "In the old style reckoning [Julian calendar], March 25 was the beginning of the year. After the adoption of the new style, or Gregorian calendar, January 1 was taken as the beginning of the year and double dates are often used to indicate the time between Jan. 1 and Mar. 25. (pp. 22-23)

Therefore, Mary Rowlandson was captured on February 10, 1675 according to the OS (Julian) calendar which would have been the calendar she used. Once the Gregorian calendar replaced the Julian, the date would have fallen in that January 1 through March 25 range. So subsequent historians would designate the event as happening in 1675/76.

Reference: Wells, D. W. and R. F. Wells. 1910. A History of Hatfield Massachusetts.

F.C.H. Gibbons, Springfield, Massachusetts.