As a beginning student of Genealogy, there tends to be confusion as to why so many dates are given with two different years i.e. 1752/53. At a glance, these double dates appear to be an expression of uncertainty. However, these double dates are an accurate representation of the period of adjustment from the Julian to the Gregorian calendars. Beginning in 1752 with the adoption of the Gregorian Calendar by England and her colonies, dates were maintained in either format. Reasonable conjecture leads us to believe that this double date system should be considered accurate for the lifespan of the entire generation living in 1752. Unless the researcher has definitive proof as to which calendar a particular civil administration, church, or family employed for chronology, dates prior to 9/14/1752 should expressed as double dates. And, all dates within a one year span for the generations living in 1752 should be considered as accurate.
Quoted from Peter Meyers, The Julian and Gregorian Calendars by Peter Meyer, 10 December 2004 <http://www.hermetic.ch/cal_stud/cal_art.html> 3 January 2005.
The average length of a year in the Julian Calendar is 365.25 days (one additional day being added every four years). This is significantly different from the "real" length of the solar year. . . .The average length of a year in the Julian Calendar is 365.25 days (one additional day being added every four years). This is significantly different from the "real" length of the solar year. . . .Pope Paul III recruited several astronomers, principally the Jesuit Christopher Clavius (1537-1612), to come up with a solution. They built upon calendar reform proposals by the astronomer and physician Luigi Lilio (d. 1576). When Pope Gregory XIII was elected he found various proposals for calendar reform before him, and decided in favor of that of Clavius. On 1582-02-24 he issued a papal bull, Inter Gravissimas, establishing what is now called the Gregorian Calendar reform.
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Inter Gravissimus |
The Gregorian reform consisted of the following:
- Ten days were omitted from the calendar, and it was decreed that the day following (Thursday) October 4, 1582 (which is October 5, 1582, in the old calendar) would thenceforth be known as (Friday) October 15, 1582.
- The rule for leap years was changed. In the Julian Calendar a year is a leap year if it is divisible by 4. In the Gregorian Calendar a year is a leap year if either (i) it is divisible by 4 but not by 100 or (ii) it is divisible by 400. In other words, a year which is divisible by 4 is a leap year unless it is divisible by 100 but not by 400 (in which case it is not a leap year). Thus the years 1600 and 2000 are leap years, but 1700, 1800, 1900 and 2100 are not.
- New rules for the determination of the date of Easter were adopted.
- The position of the extra day in a leap year was moved from the day before February 25th to the day following February 28th.
The Gregorian Calendar was adopted in Britain (and in the British colonies) in 1752, with (Wednesday) September 2, 1752, being followed immediately by (Thursday) September 14, 1752. . . .With the introduction of the Gregorian Calendar in Britain and the colonies New Year's Day was generally observed on January 1. Previously in the colonies it was common for March 24 of one year to be followed by March 25 of the next year. This explains why, with the calendrical reform and the shift of New Year's Day from March 25 back to January 1, the year of George Washington's birth changed from 1731 to 1732. In the Julian Calendar his birth date is 1731-02-11 but in the Gregorian Calendar it is 1732-02-22.
Key Events:
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755 BCE Roman calendar dates begin: ab urbe condita (from the founding of the city)
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239 BCE Alexandrian Aristarchus' Calendar adopted in Egypt
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46 BCE Rome adopts the Julian Calendar (identical to the Alexandrian Aristarchus' Calendar)
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2/24/1582 Roman Catholic Church adopts the Gregorian Calendar
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9/14/1752 England adopts the Gregorian Calendar