Galileo Galilei (15 February 1564 Drake . The date of Galileo's birth is given according to the Julian calendar, which was then in force throughout the whole of Christendom. In 1582 it was replaced in Italy and several other Catholic countries with the Gregorian calendar. Unless otherwise indicated, dates in this article are given according to the Gregorian calendar. – 8 January 1642) by John Gerard. Retrieved 11 August 2007 was a Tuscan (Italian) physicist, mathematician, astronomer, and