Question: When was the Dutch artist who was part of Art Concret born? 
Context: Roelof Paul Citroen (15 December 1896 – 13 March 1983) was a German-born Dutch artist, art educator and co-founder of the New Art Academy in Amsterdam.  Among his best-known works are the photo-montage Metropolis and the 1949 Dutch postage stamps. The Dutch artist Otto van Rees (1884-1957), son of a family of academics, started his career in Paris, where he moved in 1904.  By intermediation of Picasso, whom Van Rees met in the café Le Lapin Agile, Van Rees put up at an atelier in the Bateau Lavoir.  At the Académie Carrière he became friends with George Braque.  The Bateau Lavoir was a lively place where his contact with other artists, painters, (Picasso, Léger, Gris, Van Dongen) as well as writers (Max Jacob, Blaise Cendrars, Apollinaire) deepened.  His wife and fellow artist, Adya van Rees-Dutilh joint him soon after.  Paris would be their winter residence on and off for over 30 years.  Some of his fellow artists became dear friends over many years: Severini, Segal, Freundlich, Mondriaan, Arp, Zadkine.  The summers were spent at Fleury-en-Bière, a little town next to Barbizon.  Kees van Dongen spent the summer of 1905 there, together with Otto and Adya van Rees in the farmhouse Van Rees rented.  They painted together in the fields around the village.  Picasso was also a visitor, as well as other artists: Otto Freundlich, Marc Chagall and Blaise Cendrars to mention a few.  After a stay in Italy his first grand exposition of 48 luministic paintings was held in 1908 in Rotterdam at the Oldenzeel gallery, gallery famous for its exhibitions (1892-1904) of works by Vincent van Gogh.  In Paris, during the early years, Otto van Rees exhibited his work at the gallery of Berthe Weil and Clovis Sagot and at the yearly Salon des Artistes Indépendants.  He also had part in the Sonderbund, Cöln in 1912 and the famous exhibition of Der Sturm in 1913.  In 1912-1916 the art of Van Rees went through changes, pointillism and luminism lost his interest.  His work evolved from physic cubism, as Apollinaire described it, to analytic cubism.  One of the first collectors of his art then was Arthur Jerôme Eddy.  During the first world war Van Rees changed his French summer residence for Ascona, little town at the Lago Maggiore.  The artistic and anarchistic colony there was inspiring.  With Arp, who later spent Christmastime 1915 at the Van Rees, Otto and Adya held the famous exposition of November 1915 at the gallery Tanner in Zürich.  This exposition is now seen as the beginning of Dada-Zürich.  The art dealer Henri Kahnweiler named Van Rees as an artist that brought the collage technique from Paris to Zürich as the start of Dada Art.  Ascona would keep Van Rees’ preference.  In 1928 Otto van Rees constructed a house on the hills there.  The house had a ground plan of a circle and a square, announcing the famous 1930 collective art show of Cercle et Carré.  After the tragic death of their oldest daughter, killed in a train accident in France, Otto van Rees spent more and more time in Holland.  He moved there in 1934.  In Holland the young painters called him their Nestor, who taught them the profound values on art.  Many public buildings in Holland: churches, railway station, courthouse, ministry, theatres were embellished by his mural paintings . Concrete art is an art movement with a strong emphasis on abstraction.  The artist Theo van Doesburg, closely associated with the De Stijl art movement, coined the term "concrete art" as he in 1930 founded the group Art Concret and articulated its features in a manifesto titled "The Basis of Concrete Art", signed by four other artists of the group, including Otto G. Carlsund, Jean Hélion and Leon Tutundjian.  The manifesto explained that the resultant art should be non-referential insofar as its components should "not" refer to, or allude to, the entities normally encountered in the natural, visible world.  This is a distinction from abstraction generally.  In a more general sense "abstract art" could and often does include the "abstraction of forms in nature".  But "concrete art" was intended to emanate "directly from the mind" and consequently to be more "cerebral" than abstract art generally.  Concrete art is often composed of basic visual features such as planes, colors, and forms.  "Sentiment" tends to be absent from concrete art.  The "hand" of the artist may be difficult to detect in finished works of concrete art; concrete art may appear, in some instances, to have been made by a machine.  Concrete art often has a core visual reference to geometry whereas more general abstract art may find its basis in the components of the natural world.  A formulation of a description of concrete art might include a considerable reliance on the formal qualities of an artwork.  Theo Van Doesburg's manifesto stated that art "should receive nothing from nature's formal properties or from sensuality or sentimentality.  We want to exclude lyricism, dramaticism, symbolism, etc…."  In concrete art a mathematical equation can serve as a starting point.  Concrete art can include painting and sculpture. Viviane Sassen (born 1972) is a Dutch artist living in Amsterdam.  She is a photographer who works in both the fashion and fine art world.  She is known for her use of geometric shapes, often abstractions of bodies.  She has been widely published and exhibited.  She was included in the 2011 New Photography exhibit at the Museum of Modern Art.  She has created campaigns for Miu Miu, Stella McCartney, and Louis Viutton, among others.  She has won the Dutch Prix de Rome (2007) and the Infinity Award from International Center of Photography. Art Concret was an avant-garde group of artists formed in 1929 in Paris, France, championing a geometrical abstract art closely related to the aesthetics of Neo-plasticism.  It consisted of Otto G. Carlsund, Theo van Doesburg, Jean Hélion, Marcel Wantz and Léon Arthur Tutundjian. David Pierre Giottino Humbert de Superville (The Hague, July 18, 1770 - Leiden, January 9, 1849) was a Dutch artist and art scholar.  He was a draughtsman, lithographer, etcher, and portrait painter, and also wrote treatises on art, including the influential work "Essai sur les signes inconditionnels dans l'art" (Leiden, 1827).  His 1815 painting of the jurist and statesman Johan Melchior Kemper is now part of the collection of the Rijksmuseum in Amsterdam. Jan Robert Leegte (1973) is a Dutch artist who lives and works in Amsterdam.  He is one of the first Dutch artists who makes art on and for the internet since the nineties.  Nowadays, he makes art both on the internet, in the form of websites as in offline media, like prints, sculptures and projections.  A recurring theme in his work is the sculptural materiality of interfaces and computer programs, like the graphic design of cursors, menu and scroll bars. The Valkhof at Nijmegen is an oil painting by Dutch artist Aelbert Cuyp, likely painted between 1652 and 1654, during the Dutch Golden Age.  It is currently part of the permanent collection in the Indianapolis Museum of Art. Matheus Josephus Lambertus (Mathieu) Ficheroux (April 22, 1926 - October 11, 2003) was a Dutch artist, who worked as sculptor, glass painter, painter, draftsman, wall painter and installation artist.  He is considered among the foremost Dutch artist of the second part of the 20th century. Theo van Doesburg (] , 30 August 1883 – 7 March 1931) was a Dutch artist, who practiced painting, writing, poetry and architecture.  He is best known as the founder and leader of De Stijl.
Answer: 30 August 1883