<P> Because of the differences, English people and their correspondents often employed two dates, dual dating, more or less automatically . For this reason, letters concerning diplomacy and international trade sometimes bore both Julian and Gregorian dates to prevent confusion: for example, Sir William Boswell writing to Sir John Coke from The Hague dated a letter "12 / 22 Dec. 1635". In his biography of Dr John Dee, The Queen's Conjurer, Benjamin Woolley surmises that because Dee fought unsuccessfully for England to embrace the 1583 / 84 date set for the change, "England remained outside the Gregorian system for a further 170 years, communications during that period customarily carrying two dates". In contrast, Thomas Jefferson, who lived during the time that the British Isles and colonies eventually converted to the Gregorian calendar, instructed that his tombstone bear his date of birth using the Julian calendar (notated O.S. for Old Style) and his date of death using the Gregorian calendar . At Jefferson's birth the difference was eleven days between the Julian and Gregorian calendars; thus his birthday of 2 April in the Julian calendar is 13 April in the Gregorian calendar . Similarly, George Washington is nowadays officially reported as having been born on 22 February 1732, rather than on 11 February 1731 / 32 (Julian calendar). </P> <P> There is some evidence that the calendar change was not easily accepted . Many British people continued to celebrate their holidays "Old Style" well into the 19th century, a practice that according to the author Karen Bellenir reveals a deep emotional resistance to calendar reform . </P> <P> The need for change arose from the realisation that the correct figure for the number of days in a year is not 365.25 (365 days 6 hours) as supposed by the Julian calendar but almost exactly 365.2425 days (365 days 5 hours 49 minutes 12 seconds), a reduction of 10 minutes 48 seconds per year: the Julian calendar has too many leap years . The consequence was that the basis for calculation of the date of Easter as decided in the fourth century had drifted from reality . The Gregorian calendar reform also dealt with the accumulated difference between these figures, between the years 325 and 1582 (1752 in the British Empire), by skipping 10 dates (11 in the case of Great Britain, including her colonies and Ireland) to restore the date of the vernal equinox to approximately March 21, the approximate date it occurred at the time of the First Council of Nicea in 325 . </P> <P> For a ready reckoner to assist in converting O.S. dates to N.S. and vice versa, see this table . </P>

When did they change new years from march to january