Transition from the Julian to the Gregorian Calendar

Transition from the Julian to the Gregorian Calendar

Julius Caesar introduced the Julian calendar in 46 BC as a reform of the old Roman calendar. The Julian calendar was in use in Europe and Northern Africa from the times of the Roman Empire until 1582, when Pope Gregory XIII introduced the Gregorian calendar which uses the Anno Domini (AD) system, a year count that begins with the Incarnation of Jesus. When a better understanding of how to more accurately measure the length of the solar year was determined, it was realized that the Julian system exceeded the solar year by around 11 minutes. Between the years 325 and 1582, this excess amounted to 10 days, causing the vernal equinox to be incorrectly set from 21 March to 11 March. The Julian system had further misconstrued the timing of Easter, prompting the Catholic Church to adjust the calendar so Easter would be celebrated at the time the First Council of Nicaea had agreed upon in 325.

The Julian calendar had 12 months, with 3 years of 365 days, followed by a fourth year of 366 days. Since the calendar was slightly longer than the solar year, it was 10 days out of synch with the solar cycle by the year 1500. To restore proper synchronization with the seasons, the new Gregorian calendar dropped 10 days from the month of October in 1582 and to prevent the problem of extra days from occurring again, one day was added to February in every year divisible by 4 (leap year).

Pope Gregory ordered that 10 days be dropped from the calendar to restore the equinox to its proper place. Spain, Portugal, the Polish-Lithuanian Commonwealth, Italy, and France adopted the new calendar in 1582, but many Protestant countries objected the adoption of a Catholic invention and resisted calendar conversion until the 1700s. Britain and the British Empire did not adopt the Gregorian calendar until 1752.

By the year 1700, countries that continued to use the Julian calendar had fallen 11 days out of synch with the solar cycle. So, for countries converting to the Gregorian calendar in the 1700s, it became necessary to add one day in addition to the ten already added in 1582. When the British Empire adopted the Gregorian calendar in September 1752, they had to drop 11 days from September and change the New Year from 25 March to 1 January in order for their calendar to properly synchronize with the solar year. For genealogists and historians, this change is significant because it means that dates prior to 1752 that fall between 1 January and 24 March, are subject to dual dating.

For a period of 170 years (1582-1752), both dating systems were concurrently used in different parts of Western Europe and its colonies, so a system of dual dating was devised to represent the date of both the Julian and Gregorian calendar. Dual dates are identified with a slash mark between the two dates (i.e., 1712/1713). For instance, George Washington’s birthday under the old calendar was 11 February 1731, but under the new calendar became 22 February 1732. Since his birthday occurred in the 1700s prior to the 1752 conversion, and fell between 1 January and 24 March, 11 days were added to the month and the year was increased by one. To properly notate his birthday using the dual dating system, it would be written as, 11/22 February 1731/32. Dual dating can be seen in court records, wills, and on colonial gravestones or cemetery transcriptions. Since the British Empire did not adopt the Gregorian calendar until 1752, dual dating must occur for dates from 1 January to 24 March between the years 1582 and 1752. This requirement is necessary for Great Britain and all of its colonies, including colonial America. In Britain, 25 March was recognized as the first day of the year and therefore, is not dual dated.

Dual dating can also be represented by adding the notation “Old Style” (OS) and “New Style” (NS) to historical dates for identification of the calendar system used. Since Thomas Jefferson lived during the time Great Britain and its colonies converted to the Gregorian calendar, he instructed that his tombstone bear his dates of birth and death in Old Style and New Style. Below his tombstone’s epitaph is written, “Born April 2 1743 OS, Died July 4 1826.”

Converted dates that fall between the years 1582-1752

Old Style Date	New Style Date	Difference
10 JAN 1690 OS	20 JAN 1691 NS	10 days
12 FEB 1701 OS	23 FEB 1702 NS	11 days
15 MAR 1715 OS	26 MAR 1716 NS	11 days
18 APR 1723 OS	29 APR 1723 NS	No year change

Difference between Gregorian and Julian calendar dates

Gregorian Range	Julian Range	Difference
From 15 October 1582	From 5 October 1582	10 days
to 28 February 1700	to 18 February 1700	10 days
From 12 March 1700	From 1 March 1700	11 days
to 28 February 1800	to 17 February 1800	11 days
From 13 March 1800	From 1 March 1800	12 days
to 28 February 1900	to 16 February 1900	12 days
From 14 March 1900	From 1 March 1900	13 days
to 28 February 2100	to 15 February 2100	13 days
From 15 March 2100	From 1 March 2100	14 days
to 28 February 2200	to 14 February 2200	14 days

Scotland changed the start of its new year long before that of England. Since France had already converted to the new calendar, Scotland found that its trade with France was hampered by the use of a different calendar, so in 1600, the Scottish New Year was changed to 1 January. Even following the Union of the Crowns in 1603, England maintained 25 March as the beginning of the year for nearly 150 years which sometimes resulted in ambiguity in the dates of historical events. Scotland, along with England and Ireland, converted to the Gregorian calendar in 1752.

Summary of Date Conversions for Great Britain and its Colonies

For Great Britain and its American colonies, two rules of thumb must be observed for date conversions that fall between the years 1582-1752. Firstly, all Julian dates from 5 October 1582 to 22 August 1752 must have the appropriate number of days added in order to convert to the Gregorian system. If the date range is 5 October 1582 to 18 February 1700, 10 days must be added. If the date range is 1 March 1700 to 22 August 1752, 11 days must be added. Secondly, if the converted date falls between 1 January and 24 March, the year must be increased by one.

So, if the Julian (Old Style) date were 15 February 1682, the Gregorian (New Style) date would be 25 February 1683 (10 days added, plus 1 year). Similarly, if the Julian (Old Style) date were 12 January 1715, the Gregorian (New Style) date would be converted to 23 January 1716 (11 days added, plus 1 year). Finally, if the Julian (Old Style) date were 5 May 1732, the Gregorian (New Style) date would be converted to 16 May 1732 (11 days added, but the year remains the same because May is a month that does not fall between 1 January and 24 March).

Interpreting English Regnal Years

Some historical documents are dated not by the calendar year but by the regnal year – the period by which a ruling monarch served on the throne. In England and its colonies, regnal years were occasionally noted and used as time markers in addition to the calendar dates. 1 Elizabeth I means the first year of the reign of Elizabeth I. Elizabeth I came to the throne on 17 November 1558, so 1 Elizabeth I implies the period of time between 17 November 1558 and 16 November 1559.

Dating the reign of Charles II is calculated differently. Although he came to the throne in May 1660, after the Commonwealth period, he actually calculated his regnal year as beginning on 30 January 1649, the date of his father’s execution (Charles I). So documents written in the first year that Charles II was genuinely on the throne would actually be styled, 12 Charles II.

Quaker Dating Methodology

Since Quakers preferred not to use the pagan naming convention for labeling months, they numbered months numerically, one through twelve. For instance, a Quaker monthly meeting record may record that a boy was born the 12^th month, 12^th day, in 1656. Since prior to 1752 the British New Year was 25 March, March was considered the first month of the year. April was the second month, May, the third month, and so forth. The pattern was as follows:

Quaker Month	Actual Month
Month 1	March
Month 2	April
Month 3	May
Month 4	June
Month 5	July
Month 6	August
Month 7	September
Month 8	October
Month 9	November
Month 10	December
Month 11	January
Month 12	February

So, if a Quaker was born the 12^th month, 12^th day, in 1656, he was actually born February 22, 1657. The same Gregorian conversion dating rules apply to Quaker records as they do with British colonial records. Since the early Quakers were largely of English descent, they utilized the Julian system used by the British Empire until 1752. It is only the numerical naming convention that makes Quaker dating distinctly different from that of the British Empire.

Change on Scotland paragraph 5/19/2010