Understanding the Dates of Documents
Measuring time is not necessarily a straight forward process. The historical use of different calendars and the use of various ways of recording dates leads to a complexity of systems. Understanding these systems is essential though for interpreting the dates found on historical documents.
Calendars
Calendars need to align with the Earth’s orbit around the sun so that the months and seasons are synchronised and the timing of the seasons is the same every year. To do this, a calendar needs to accurately measure the time the earth completes an orbit of the sun, and here lies the problem.
The problem arises because the average time it takes the Earth to orbit the sun, which is called a solar year, is not an exact number of days. On average, a solar year is 365.2422 days, and designing a calendar that allows for the additional 0.2422 of a day has caused a few issues in the past. The design of the Julian calendar, for example, creates a year that is too long and made up of 365.25 days. The Gregorian calendar is more accurate with a year made up of 365.2425 days.
The Old Style and the New Style
Over the centuries, countries abandoned the Julian calendar to adopt the more accurate Gregorian calendar. A full list of countries and the dates they adopted the Gregorian calendar can be found here.
The first countries to adopt the Gregorian calendar, such as Italy, France, Spain and Portugal, did so in 1582. By this time, the Julian calendar was 10 days out and these additional days had to be removed when transferring to the new calendar. When England adopted the Gregorian calendar in 1752 the difference had increased to 11 days. With different countries making the switch at different times, documents written on the same day but in different countries may have different dates written on them.
For example, between 1582 and 1752, England and France were using different calendars. The English still used the Julian calendar, whilst the French had already adopted the Gregorian calendar. At this time, there was a 10 or 11 day difference between the two calendars that could lead to situations where a letter written in England in reply to a letter sent from France could be dated before the original was sent. For example, a letter written in France on 25th April 1642 (Gregorian calendar) might be replied to in England a week later, 2nd May 1642, but in England this day was 22nd April 1642 (Julian calendar).
In England, the Calendar (New Style) Act 1750 introduced changes that would allow for the adoption of the Gregorian calendar and address the deficit with the calendars of other countries. The changes included losing 11 days in September 1752 when 2nd September was followed by 14th September and 1st January became the first day of the year. Prior to this, the first day of the year was 25th March, which was partly a legacy of the Roman calendar. Under the terms of the act, the move of New Year’s Day took place after 31st December 1751. This meant that January and February 1751, which would have followed December 1751 on the Julian calendar, became the first two months of 1752. This effectively left 1751 with nine months, from 25th March 1751 to 31st December 1751.
After the changes had been made, there were two forms of dates, the Old Style (O.S.) and the New Style (N.S.). The Old Style dates, written before the change, used the Julian calendar with the first day of the year on 25th March. The New Style, written after, made use of the Gregorian calendar with 1st January as the first day of the year.
Understanding O.S. and N.S.
Having two styles may be confusing, especially if the dates are taken out of context. For example, using the Old Style dates, a child could be baptised in June 1742 and buried in January 1742 because the year in the Old Style (Julian calendar) was from 25th March – 24th March. See the child’s timeline diagram below:
Sometimes it is not always clear if dates are O.S. or N.S. but it is reasonable to assume dates written on a document before the calendar change are O.S. To help avoid confusion, a method of double dating, or dual dating, is used. For example, transcriptions of documents, such as parish registers, may use double dating in recording the year of the event. In the case of the example above, the date of the burial is January 1742/43 using the double date method. The 1742/43 notation indicates that if 25th March is considered as the start of the new year (as it would have been at the time) then the burial took place in January near the end of 1742, but if the start of the new year is considered to be 1st January then the exact same month of the burial would have fallen at the beginning of 1743 instead.
It is only dates between 1st January and 24th March that can be double dated in this way because the change to the first day of the year directly affects them. Other dates remain in the same numerical year regardless. See the child’s timeline diagram above.
Converting O.S. dates to N.S. dates is time-consuming, so it is likely that transcriptions show the date recorded at the time, in O.S. For example, a baptism dated 19th January 1714/15 took place on 19th January 1714 O.S. which is 30th January 1715 N.S. (see the section below). If written using the double dating method, the date is 19/30 January 1714/15.
Converting from O.S. to N.S.
Converting from O.S. to N.S. is fairly easy. It involves removing the additional days that the Julian calendar accumulated as time passed. The difference between the Julian calendar and Gregorian calendar is shown in the following table:
| Gregorian Date Range | Equivalent Julian Date Range | Difference |
|---|---|---|
| 15 October 1582 – 28 February 1700 | 5 October 1582 – 17 February 1700 | 10 days |
| 1 March 1700 – 28 February 1800 | 18 February 1700 – 16 February 1800 | 11 days |
| 1 March 1800 – 28 February 1900 | 17 February 1800 – 15 February 1900 | 12 days |
| 1 March 1900 – 28 February 2100 | 16 February 1900 – 14 February 2100 | 13 days |
| 1 March 2100 – 28 February 2200 | 15 February 2100 – 13 February 2200 | 14 days |
| 1 March 2200 – 28 February 2300 | 14 February 2200 – 12 February 2300 | 15 days |
Consider the birthdate of Sir Isaac Newton on 25th December 1642 O.S. At the time, the difference between the two calendars was 10 days, so this is added to the birthdate:
25th December 1642 O.S. + 10 days = 4th January 1643 N.S.
The various biographies of Isaac Newton often cite these two birthdates, for example, his Wikipedia page.
The following converter will turn O.S. dates into N.S. dates:
Regnal Years
A regnal year is a year within the reign of a monarch. On the ascension of a new monarch, a new set of regal years begin, for example “1 Geo 2” indicates the first year of George II’s reign. The start and end dates of regnal years therefore change with each monarch. Queen Victoria ascended on 20 June 1837, so each regnal year ran from 20 June to 19 June during her reign, which ended on 22 January 1901. Edward VIII then ascended, and regnal years became 22 January to 21 January.
A large collection of legal documents makes use of regnal years. Knowing the dates of the reigns of monarchs helps to date them without too much difficulty. The act of parliament that introduced the calendar changes of 1752, is the Calendar (New Style) Act 1750 and referenced 24 Geo. 2. c. 23 (Chapter 23 of the 24th regnal year of George II).
The tool below converts dates between the Gregorian calendar and regnal year notation.
Easter
Sometimes the dates on documents relate to Easter which is a moveable feast because its date differs each year. Roughly, it falls on the first Sunday after the full Moon that occurs on or after the spring equinox.
The following form provides Easter dates from 1200 onwards:
A list of Easter dates can also be found on the GENUK website.
Quarter Days
Quarter days were historically significant dates in the UK, used for a variety of administrative, financial, and legal purposes. They marked the division of the year into quarters and were essential for the payment of rents, interest, and other financial obligations, including legacies stipulated in wills. In England and Wales the four days were:
Lady Day (25th March) – This marked the Feast of the Annunciation and was the start of the year until 1752. It was the beginning of many financial cycles, which moved to 05 April in 1753 following the introduction of the Gregorian calendar. Rent and contracts often commenced on Lady Day.
Midsummer Day (24th June) – Also known as the Feast of St. John the Baptist, it falls close to the summer solstice and midsummer celebrations. Midsummer fairs provided a social and commercial hub for communities, so this was another key date for rent payments and agricultural agreements.
Michaelmas Day (29th September) – The Feast of St. Michael and All Angels. It coincided with the end of the harvest and the beginning of the new farming cycle. It was therefore a crucial date for financial settlements, hiring fairs, and the commencement of many legal and financial agreements.
Christmas Day (25th December) – A major religious and cultural holiday. Although primarily a religious and family holiday, Christmas was also a key date for financial transactions and the settlement of accounts before the year-end.
In Scotland, the traditional quarter days differed slightly:
- Candlemas (2nd February)
- Whitsunday (15th May)
- Lammas (1st August)
- Martinmas (11th November)
