Despite being born on January 4, he was born on Christmas day
I know, confusing. At the time of his birth, the Gregorian calendar hadn’t been adopted by England yet (it took them until 1752, and Newton was born in 1643). Records indicate that Isaac was born on Christmas and baptized on New Year’s Day. When the Gregorian calendar was finally adopted by England, it needed adjusted by 11 days, making January 4 Isaac’s recognized birthday.