Adoption of the Gregorian calendar the Empire (except Scotland, which had already done so from 1600) changed the start of the civil year from 5 April to 1 January. Consequently, the custom of dual dating (giving a date in both old and new styles) can refer to the Julian/Gregorian calendar change, or to the start of year change, or to both. The British tax year traditionally began on Lady Day (25 March) on the Julian calendar and thus became 5 April, which was the "Old Style" equivalent. A 12th skipped Julian leap day in 1800 changed its start to 6 April. It was not changed
Gregorian calendar the start of the year, and also aligned the British calendar with the Gregorian calendar, there is some confusion as to what these terms mean. They can indicate that the start of the Julian year has been adjusted to start on 1 January (NS) even though contemporary documents use a different start of year (OS); or to indicate that a date conforms to the Julian calendar (OS), formerly in use in many countries, rather than the Gregorian calendar (NS). Extending the Gregorian calendar backwards to dates preceding its official introduction produces a proleptic calendar, which should be used with some