In England and Wales, the legal year 1751 was a short year of 282 days, running from 25 March to 31 December.
To align the calendar to the sun and to that used on the continent since 1582, England changed from using the Julian to the Gregorian calendar: and the calendar was advanced by 11 days: Wednesday 2 September 1752 was followed by Thursday 14 September 1752.
The year 1752 was thus also a short year (355 days).
Dates before 1752 are often shown using the double date format. Thus 15 February 1715, near the end of the year in England (which was 15 February 1716, near the beginning of the next year in Scotland) is written as 15 Feb 1715/16.
For why the tax year starts on 6 April see here.
In some years after 1752 the person making the entries in the registers seems to revert to the old pre-1752 start of year. In the example shown here burials for 1778 run from March 29th to March 16th. This seems to have happened from 1766 to 1780.
In one register (HP44/1/3/4 pages 51-58) there are entries at the back for " burials in woollen", from 1678-80. This was according to the law of the time to support the wool industry.
The Burial in Woollen Acts 1666-80 were Acts of Parliament which required the dead to be buried in pure English woollen shrouds to the exclusion of any foreign textiles. It was a requirement that an affidavit be sworn in front of a Justice of the Peace (usually by a relative of the deceased), confirming burial in wool.
Sometimes months are given as numbers, for example 7r. However this is not the modern month number – it stands for September (the Latin for 7 is septem).
Similarly 8r is October (Latin for 8 is octo), 9r is November (Latin for is novem), Xr is December (Latin for 10 or X is decem).