Isaac Newton (tí wọ́n bí ní Ọjọ́ kẹrin oṣù kìíní ọdún 1643 - ọjọ́ kọkànlélọ̀gbọ̀n oṣù kẹta 1727) jẹ́ onímọ̀ sáyẹ́nsì ọmọ orílẹ̀-èdè Gẹ̀gẹ̀ẹ́sì. Ó jẹ́ amọ̀ye ninu ẹ̀kọ́ ìsirò, awòràwọ̀, ẹ̀sìn àti ònkòwé. Ní ìgbà ayé rẹ̀, wọ́ń mọ si amọ̀ye ohun gbogbo. Látìnì: Philosophiæ Naturalis Principia Mathematica, ìwé ti ó kọ ní ọdún 1687 jẹ́ ìpìlẹ̀ fun ìsisẹ́ẹ̀ro ayébáyé (nínu ẹkọ́ọ físíìsì). Ìwé yìí wà nípa òfin ìsirò lóri ìmọ̀ye ìṣẹ̀dá, ó sìm jẹ́ awọn ofin akọ́kọ́. During Newton's lifetime, two calendars were in use in Europe: the Julian or 'Old Style' in Britain and parts of northern Europe (Protestant) and eastern Europe, and the Gregorian or 'New Style', in use in Roman Catholic Europe and elsewhere. At Newton's birth, Gregorian dates were ten days ahead of Julian dates: thus Newton was born on Christmas Day, 25 December 1642 by the Julian calendar, but on 4 January 1643 by the Gregorian. By the time he died, the difference between the calendars had increased to eleven days.