Gaston Maurice Julia (3 February 1893 – 19 March 1978) was a French mathematician who devised the formula for the Julia set.
 His works were popularized by French mathematician Benoit Mandelbrot; the Julia and Mandelbrot fractals are closely related.
Évariste Galois (] ; 25 October 1811 – 31 May 1832) was a French mathematician born in Bourg-la-Reine.
 While still in his teens, he was able to determine a necessary and sufficient condition for a polynomial to be solvable by radicals, thereby solving a problem standing for 350 years.
 His work laid the foundations for Galois theory and group theory, two major branches of abstract algebra, and the subfield of Galois connections.
 He died at age 20 from wounds suffered in a duel.
Denis (sometimes Didier) Henrion, was a French mathematician born at the end of the 16th century in France.
 He co-edited the works of Viète.
 He died around 1632 in Paris.
Henri Paul Cartan (] ; July 8, 1904 – August 13, 2008) was a French mathematician with substantial contributions in algebraic topology.
 He was the son of the French mathematician Élie Cartan and the brother of composer Jean Cartan.
Bernard Frénicle de Bessy (c. 1604 – 1674), was a French mathematician born in Paris, who wrote numerous mathematical papers, mainly in number theory and combinatorics.
 He is best remembered for "Des quarrez ou tables magiques", a treatise on magic squares published posthumously in 1693, in which he described all 880 essentially different normal magic squares of order 4.
 The Frénicle standard form, a standard representation of magic squares, is named after him.
 He solved many problems created by Fermat and also discovered the cube property of the number 1729 (Ramanujan number), later referred to as a taxicab number.
Pascal's law (also Pascal's principle or the principle of transmission of fluid-pressure) is a principle in fluid mechanics that states that a pressure change occurring anywhere in a confined incompressible fluid is transmitted throughout the fluid such that the same change occurs everywhere.
 The law was established by French mathematician Blaise Pascal in 1647–48.
Arthur Harold Stone (30 September 1916 – 6 August 2000) was a British mathematician born in London, who worked mostly in topology.
 His wife was American mathematician Dorothy Maharam.
 His first paper dealt with squaring the square, he proved the Erdős–Stone theorem with Paul Erdős and is credited with the discovery of the first flexagon, a trihexaflexagon while he was a student at Princeton University in the USA in 1939.
 The Stone's metrization theorem has been named after him, and he was a member of a group of mathematicians who published pseudonymously as Blanche Descartes.
 He is not to be confused with American mathematician Marshall Harvey Stone.
Louis Bertrand Castel (5 November 1688 – 11 January 1757) was a French mathematician born in Montpellier, who entered the order of the Jesuits in 1703.
 Having studied literature, he afterwards devoted himself entirely to mathematics and natural philosophy.
 After moving from Toulouse to Paris in 1720, at the behest of Bernard de Fontenelle, Castel acted as the science editor of the Jesuit "Journal de Trévoux".
Blaise Pascal ( ; ] ; 19 June 1623 – 19 August 1662) was a French mathematician, physicist, inventor, writer and Catholic theologian.
 He was a child prodigy who was educated by his father, a tax collector in Rouen.
 Pascal's earliest work was in the natural and applied sciences where he made important contributions to the study of fluids, and clarified the concepts of pressure and vacuum by generalising the work of Evangelista Torricelli.
 Pascal also wrote in defence of the scientific method.
In mathematics, Pascal's triangle is a triangular array of the binomial coefficients.
 In much of the Western world, it is named after French mathematician Blaise Pascal, although other mathematicians studied it centuries before him in India, Persia (Iran), China, Germany, and Italy.

Question: When was the French mathematician born who established Pascal's law?
Answer: 19 June 1623