You may be interested in, even fascinated by, three things affecting dates. It is impossible to tell whether many of the dates in the imported data always take this into account. However, since in many instances we are talking about a difference of just one year it is hardly worth losing sleep over it! But for your edification:

First, dates were at one time identified as "in the Xxx year of King Nnn" or, using Latin, "anno Xxx Nnn", in which case you need to know when a sovereign assumed and left office - see Kings and Queens of England: a reference chart for regnal calendars, which lists the reigns of English monarchs. Thus "anno 38 Henry 3" in the notes of Robert de Hougham II is the thirty-eighth year of the reign of Henry III, or 1253 or 1254, depending on what month - see the next paragraph.

Second, the year changed on 25 March - in England, at least. So, 24 March in year x comes after 25 March in year x!! Researchers indicate the year in this period 1 Jan-24 Mar as, say, 1253/54 (as in the notes of Robert de Hougham II).

September 1752 Su Mo Tu We Th Fr Sa 1 2 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

So if that voice from the ouija board during the séance tells you they were born in England on 13 Sep 1752, you'll know it's a scam! There is no 13 Sep 1752 in English history.

The Gregorian Calendar reform also changed the start of the year to 1 January. Now, think about it - 12 days went missing in September 1752, but with the change to 1 January as the start of the year, nearly three months of dates went missing also! 1 January-24 March 1752 don't exist in English history, since, for the first time, the day after 31 Dec 1752 was 1 Jan 1753. Mind you, this start-of-the-year thing did not suddenly become an issue in England in 1752. Check out the monument erected before 1714 in St Mary's Sandwich to Solomon Hougham on which his second son, also Solomon, is recorded as having died on "March the 16, 1696/7".

Now, just to show how challenging this can get for family tree researchers, Scotland adopted the Gregorian calendar at the same time as England did (1752) - but had decided way back in 1600 to start the year on 1 January while still using the olde calendar. I guess that means that the dates 1 Jan - 24 Mar 1599 do not exist in Scottish history.

Check out

• Toke Nørby's Perpetual Calendar offers a list of countries and when they changed from Julian to Gregorian.
• The Calendar FAQ - gives an overview of the Christian, Hebrew, Persian, and Islamic calendars in common use, and provides a historical background for the Christian calendar, plus an overview of the French Revolutionary calendar, the Maya calendar, and the Chinese calendar.
• Old Style and New Style Dates for genealogists
• Old Style (OS) and New Style (NS) dates
• Ian's English Calendar allows you to calculate dates based on "regnal" years, or the reigning years of an English monarch, as discussed above
• and for a plethora of calendar links Cyndi's List - Calendar

And to cause utter confusion at a dinner or party, introduce this to the conversation: Calendars were traditionally ordinal (e.g. the thirtieth year of King John's reign) and not cardinal (King John reigned 29 years when his thirtieth year began). This is why there is no year zero in our calendar. Nowadays we count centuries as ordinal (this is the 21st century), but we think of years as cardinal (2004) even though they were originally ordinal (2004th). We certainly count birthdays as cardinal - you celebrate the beginning of your second year as your first birthday and we say that you are one year old rather than that you are in your second year. Our confusion on this derives largely from the introduction of Arabic numerals and the concept of zero to the West somewhere about 800 CE. See wordiq.com. There is also a whole book on the subject of "0": Zero by Charles Seife, published 2000 by The Publishing Mills

Information on British censuses 1841-1901

Dates

Each census records those in each household on census night. The head of the household filled in a return which was collected by the enumerator on the Monday after census night. If the householder could not write, the enumerator completed the form for him. Censuses were taken on the night of Sunday/Monday as follows:

1841 - 6th June
1851 - 30th March
1861 - 7th April
1871 - 2nd April
1881 - 3rd April
1891 - 5th April
1901 - 31st March

Information from the census

The 1841 census records names, the occupation of the head of the household, approximate ages, and whether each person was born in the county, Y(es) or N(o). In 1841, ages were recorded in months for babies up to one year old, and in years for children up to fifteen. After fifteen, ages were rounded down to the nearest 5 or 0, e.g. thirty four is recorded as 30, and twenty nine as 25. From 1851 onwards, the census enumerators asked for accurate ages, and also recorded additional information - relationship to the head of the household, marital status, and place of birth, where known.