The Julian Calendar was in use in England before 1752.
The New Year was celebrated on 1st January as it is today,
but for offical business, the date was 25th March (also known as Lady Day.)
So in the records, if someone was born in January, February or up to 24th March,
they may have 2 years of birth. The first was the year using the Julian system, and
the second year mentioned will be using the modern Gregorian Calendar.
Because of the switch over in 1752, 1751 was a short year, and only ran from 25th March 1751 to 31st December 1751.
The New Year started on January 1st 1752 (The Gregorian Calendar)
There was a further adjustment in September 1752, when 11 days were taken out of the month
to bring the New Calendar in line with the other countries that had long since adopted the Gregorian calendar, such as France and Scotland.
Because of this missing 11 days, the tax man who usually collected taxes on Lady Day, added the missing 11 days to the end of the 1752-1753 tax year,
which moved the tax date from Lady Day to 6th April, as the start of the new financial year (as it is today.)
Half way through the old year, from Lady Day to Lady Day, was 29 September (known as Michaelmas)
and this half way point was used by the church, to collate their records of baptisms, marriages & burials
to send to the Archdeacon at Canterbury Cathedral. So each yearly return document will show the
events for Michaelmas to Lady Day of one year, and Lady Day to Michaelmas of the next year.
Occasionally a 6 monthly report was sent.
When it comes to dating Wills and Archdeacon Court documents, many show dates according to the year
of the reign of a monarch.
e.g. Twentieth Five yeare of the reign of our Sovereign Lord King James of England, Ireland & France etc.
To help figure out the date, please see click on the Monarch's List. for the years of reign to help you out.
From 1752, if you want to know what day of the week a particular date was, then the website www.timeanddate.com holds all the 14 possible
calendars. The same website Click has a page to calculate number of years, months and days between two given dates.