Humanities › History & Culture Getting the Date Right How to Read & Convert Dates in Old Documents and Records Share Flipboard Email Print Getty / Marco Marchi History & Culture Genealogy Basics Surnames Genealogy Fun Vital Records Around the World American History African American History African History Ancient History and Culture Asian History European History Inventions Latin American History Medieval & Renaissance History Military History The 20th Century Women's History View More By Kimberly Powell Genealogy Expert Certificate in Genealogical Research, Boston University B.A., Carnegie Mellon University Kimberly Powell is a professional genealogist and the author of The Everything Guide to Online Genealogy. She teaches at the Genealogical Institute of Pittsburgh and the Salt Lake Institute of Genealogy. our editorial process Kimberly Powell Updated March 17, 2017 Dates are a very important part of historical and genealogical research, but they also aren't always as they appear. For most of us, the Gregorian calendar in common use today is all we encounter in modern records. Eventually, however, as we work back in time, or delve into religious or ethnic records, it is common to encounter other calendars and dates with which we aren't familiar. These calendars can complicate the recording of dates in our family tree, unless we can accurately convert and record the calendar dates into a standard format, so that there is no further confusion. Julian vs. Gregorian Calendar The calendar in common use today, known as the Gregorian calendar, was created in 1582 to replace the previously used Julian calendar. The Julian calendar, established in 46 B.C. by Julius Caesar, had twelve months, with three years of 365 days, followed by a fourth year of 366 days. Even with the extra day added every fourth year, the Julian calendar was still slightly longer than the solar year (by about eleven minutes per year), so by the time the year 1500 rolled around, the calendar was ten days out of sync with the sun. To remedy the deficiencies in the Julian calendar, Pope Gregory XIII replaced the Julian calendar with the Gregorian calendar (named after himself) in 1582. The new Gregorian calendar dropped ten days from the month of October for the first year only, to get back in sync with the solar cycle. It also retained the leap year every four years, except century years not divisible by 400 (to keep the accumulation problem from recurring). Of primary importance to genealogists, is that the Gregorian calendar was not adopted by many protestant countries until much later than 1592 (meaning they also had to drop a varying number of days to get back in sync). Great Britain and her colonies adopted the Gregorian, or "new style" calendar in 1752. Some countries, such as China, did not adopt the calendar until the 1900's. For each country in which we research, it is important to know on what date the Gregorian calendar came into effect. The distinction between the Julian and Gregorian calendar becomes important for genealogists in cases where a person was born while the Julian calendar was in effect and died after the Gregorian calendar was adopted. In such cases it is very important to record dates exactly as you found them, or to make a note when a date has been adjusted for the change in calendar. Some people choose to indicate both dates - known as "old style" and "new style." Double Dating Before the adoption of the Gregorian calendar, most countries celebrated the new year on March 25th (the date known as the Annunciation of Mary). The Gregorian calendar changed this date to January 1st (a date associated with the Circumcision of Christ). Because of this change in the start of the new year, some early records used a special dating technique, known as "double dating," to mark dates which fell between January 1 and March 25. A date such as 12 Feb 1746/7 would indicate the end of 1746 (Jan 1 – March 24) in the "old style" and the early part of 1747 in the "new style". Genealogists generally record these "double dates" exactly as found to avoid possible misinterpretation. Next > Special Dates & Archaic Date Terms << Julian vs. Gregorian Calendars Feast Days & Other Special Dating Terms Archaic terms are common in older records, and dates don't escape this usage. The term instant, for example, (e.g. "in the 8th instant" refers to the 8th of this month). A corresponding term, ultimo, refers to the previous month (e.g. "the 16th ultimo" means the 16th of last month). Examples of other archaic usage you may encounter include Tuesday last, referring to the most recent Tuesday, and Thursday next, meaning the next Thursday to occur. Quaker-Style Dates Quakers typically did not use the names of the months or days of the week because most of these names were derived from pagan gods (e.g. Thursday came from “Thor’s Day”). Instead, they recorded dates using numbers to describe the day of the week and month of the year: [blockquote shade="no"]7th da 3rd mo 1733 Converting these dates can be especially tricky because the Gregorian calendar change must be taken into account. The first month in 1751, for example, was March, while the first month in 1753 was January. When in doubt, always transcribe the date exactly as written in the original document. Other Calendars to Consider When researching in France, or in countries under French control, between 1793 and 1805, you'll probably encounter some strange looking dates, with funny-sounding months and references to the "year of the Republic." These dates reference the French Republican Calendar, also commonly referred to as the French Revolutionary calendar. There are many charts and tools available to help you convert those dates back into standard Gregorian dates. Other calendars you may encounter in your research include the Hebrew calendar, the Islamic calendar and the Chinese calendar. Date Recording for Accurate Family Histories Different parts of the world record dates differently. Most countries write out a date as month-day-year, while in the United States the day is commonly written before the month. This makes little difference when the dates are written out, as in the above examples, but when you run across a date written 7/12/1969 it is hard to know whether it refers to July 12th or December 7th. To avoid confusion in family histories, it is standard convention to use the day-month-year format (23 July 1815) for all genealogical data, with the year written out in full to avoid confusion about which century it refers to (1815, 1915 or 2015?). Months are generally written out in full, or using standard three-letter abbreviations. When in doubt about a date, it is generally best to record it exactly as written in the original source and include any interpretation in square brackets.