Most modern references note James Cook’s date of birth as 27 October 1728, however, there are some who believe the correct date is 7 November 1728. Who is right?
Well it depends on whose calendar you are using.
Cook was born in the period before the adoption of the Gregorian calendar in Great Britain and his date of birth by the Julian
calendar was 27 October. In 1750, Britain passed the Calendar (New Style) Act and from 1752 transitioned to the Gregorian calendar. By the 18th century the difference between the Julian and Gregorian calendars was 11 days.
In simple terms, to convert Cook’s Julian calendar birth date to a Gregorian calendar date we need to add 11 days. Which gives the date 7 November 1728.
However, the Calendar Act which came into effect in January 1752 was not retrospective. To quote the salient clause of the Act:
and that all Acts, Deeds, Writings, Notes and other Instruments of what Nature or Kind soever, whether Ecclesiastical or Civil,
Publick or Private, which shall be made, executed or signed, upon or after the said first Day of January 1752, shall bear Date
according to the said new Method of Supputation
The idea was to bring the calendar back into alignment with the seasons, and for practical purposes of planning and efficiency, to have common agreement throughout Britain and the dominions that the year started on 1 January. The Act was progressive and did not seek to change the past, and from that perspective we believe the correct date of Captain Cook’s birth is 27 October 1728.
Dr Nigel Erskine
Curator, Exploration & European Settlement