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Calendar & Dating Information

When the Calendar was Changed and Who was Responsible

At the time of the settling of New England in America, the New Year began on the 25th of March. Thus, March 24th was in 1599 and March 25th in 1600.

Later, a new form of designating the New Year was adopted and the first time it was used was in the General Court of Connecticut as "this 20th day of March, 1649-50, or 1650 by our present system of reckoning. This style prevailed for almost 100 years. Due to an error in the calendar, the dates in all months between 1600 and 1700 should be carried forward ten (10) days. Thus, July 10 was really July 20, according to our present system.

The British Parliament changed the calendar from the old style to the new, the one used today, and changed the date of September 3rd, 1752 (old calendar) to September 14, 1752 (new calendar) thus dropping eleven days.

Calendar Switch and Double Dates

Beginning in 45 B.C., many parts of the world used the Julian calendar to mark the passage of time. By the Julian calendar, March 25 was the first day of the year and each year was 365 days and 6 hours long. In 1582, Pope Gregory XIII determined that the Julian calendar was incorrect: each day was just a little bit too long and the human calendar wasn't keeping up with nature's calendar. To solve the problem, Pope Gregory XIII created what is known as the Gregorian calendar. This new calendar changed the first day of the year to January 1 and also jumped ahead by 10 days to make up for the lost time.

The practice of double dating resulted from the switch from the Julian to the Gregorian calendar. Not all countries and people accepted this new calendar at the same time. England and the American colonies didn't officially accept it until 1752. Before that date, the government observed March 25 as the first of the year, but most of the population observed January 1 as the first of the year. For this reason, many people wrote dates falling between January 1 and March 25 with both years, as in the following examples.

Julian or Old Style
December 25, 1718
January 1, 1718
February 2, 1718
March 20, 1719
March 25, 1718

Gregorian or New Style
December 25, 1718
January 1, 1719
February 2, 1719
March 20, 1719
March 25, 1719

Double Date
December 25, 1718
 January 1, 1718/19
February 2, 1718/19
March 20, 1718/19
March 25, 1719

By the time England and the colonies adopted the new calendar, the discrepancy between the calendars was eleven days. To resolve the discrepancy, the government ordered that September 2, 1752 be followed by September 14, 1752. Some people also added 11 days to their birth dates (a fact which is not noted on their birth certificates). You should also watch for dates that are recorded as double dates even after all calendars had officially switched. People sometimes accidentally wrote double dates.

Marriage Banns and Intentions

Church records often list the date on which a couple makes the announcement that they intend to marry. These are called marriage banns. In addition, you can find marriage intentions, which were non-religious public announcements of the couple's intention to marry. Don't misinterpret the dates of marriage banns and marriage intentions as the actual wedding date.

Date Formats

When you look at records from other countries, you should be aware of the date format that they use. In the United States, we normally write dates with the month first, the day second, and the year last. For example, we write October 15, 1970 as 10/15/70. However, many other countries reverse the order of the month and day. They write October 15, 1970 as 15/10/70. Since there are only twelve months in the year it is often easy to tell which date format was used because one of the first two numbers is greater than twelve, as in the example above. If neither of the first two dates is greater than twelve, it is harder to tell which format was used. For example, April 3, 1970 can be written as both 4/3/70 and 3/4/70. If you run into this problem, take a few moments to look at other dates in that group of records. You should eventually run across a date where one of the first two numbers is greater than twelve, and then you'll know the answer to your question.

8870 Formula for Determining Birthdates

Use this formula when the tombstone lists no date of birth, but does list the date that a person died - say May 6, 1889 and was 71 yr, 7mo, 9 days old. In order to arrive at the birthdate, one has only to use the 8870 formula to quickly get the date of birth rather than taking time to count backward.

The 8870 formula using the above date and age as an example:

Date of death - 1889 May 6 = 18890506 (where 1889=year, 05=month, 06=day)
Age at death - 71 yrs 7 mo 9 days = 710709 (where 71=years, 07=months, 09=days)
Subtract 710709 from 18890506 =18179797
Subtract the Constant (8870) from 18179797
Result = 18170927 (where 1817 = year, 09 = month, 27 = day. This person was born 27 Sep 1817)
If the age in months and age in days are less than the month and day in the date of death, you can just subtract directly, i.e.,

Date of death - 1868 Dec 25
Age at death - 45 yrs. 5 mo 4 days
Subtract 45 from 1868 = 1823
Subtract 5 from 12 = 7
Subtract 4 from 25 = 21
Result = 1823 Jul 21 or the date of birth

Page content reviewed and/or updated by the Advisory Board 2022 Dec

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