Question: Given the information above, before what date was the Schoen-Yau conjecture disproved?
Context: Shing-Tung Yau ( ; ; born April 4, 1949) is a Hong Kong and naturalised American mathematician.  He was awarded the Fields Medal in 1982.  He is currently the William Caspar Graustein Professor of Mathematics at Harvard. In mathematics, Blattner's conjecture or Blattner's formula is a description of the discrete series representations of a general semisimple group "G" in terms of their restricted representations to a maximal compact subgroup "K" (their so-called "K"-types).  Harish-Chandra orally attributed the conjecture to Robert J Blattner as a question Blattner raised, not a conjecture made by Blattner.  Blattner did not publish it in any form.  It first appeared in print in , where it was first referred to as "Blattner's Conjecture," despite the results of that paper having been obtained without knowledge of Blattner's question and notwithstanding Blattner's not having made such a conjecture.  mentioned a special case of it slightly earlier.  proved Blattner's formula in some special cases, showed that Blattner's formula gave an upper bound for the multiplicities of "K"-representations, proved Blattner's conjecture for groups whose symmetric space is Hermitian, and proved Blattner's conjecture for linear semisimple groups.  Blattner's conjecture (formula) was also proved by by infinitesimal methods which were totally new and completely different from those of Hecht and Schmid (1975).  Part of the impetus for Enright’s paper (1979) came from several sources: from , , .  In Enright (1979) multiplicity formulae are given for the so-called mock-discrete series representations also.  used his ideas to obtain deep results on the construction and classification of irreducible Harish-Chandra modules of any real semisimple Lie algebra. The Ragsdale conjecture is a mathematical conjecture that concerns the possible arrangements of real algebraic curves embedded in the projective plane.  It was proposed by Virginia Ragsdale several years after 1900 and was disproved in 1979. In algebraic topology, the doomsday conjecture was a conjecture about Ext groups over the Steenrod algebra made by Joel Cohen, named by Michael Barratt, published by and disproved by .  stated a modified version called the new doomsday conjecture. In mathematics, the Schoen–Yau conjecture is a disproved conjecture in hyperbolic geometry, named after the mathematicians Richard Schoen and Shing-Tung Yau. Legendre's conjecture, proposed by Adrien-Marie Legendre, states that there is a prime number between "n" and ("n" + 1) for every positive integer "n".  The conjecture is one of Landau's problems (1912) on prime numbers; as of 2017 , the conjecture has neither been proved nor disproved. Ernest Tilden Parker (1926–1991) was a professor emeritus of The University of Illinois.  He is notable for his breakthrough work along with R. C. Bose and S. S. Shrikhande in their disproof of the famous conjecture made by Leonhard Euler dated 1782 that there do not exist two mutually orthogonal latin squares of order 4"n" + 2 for every "n".  He was at that time employed in the UNIVAC division of Remington Rand, but he subsequently joined the mathematics faculty at The University of Illinois.  In 1968, he and a Ph.D. student, K. B. Reid, disproved a conjecture on tournaments by Erdős and Moser. In mathematics, the von Neumann conjecture stated that a group "G" is non-amenable if and only if "G" contains a subgroup that is a free group on two generators.  The conjecture was disproved in 1980. Euler's conjecture is a disproved conjecture in mathematics related to Fermat's last theorem.  It was proposed by Leonhard Euler in 1769.  It states that for all integers "n" and "k" greater than 1, if the sum of "n" "k" th powers of positive integers is itself a "k" th power, then "n" is greater than or equal to "k" . Kalman's conjecture or Kalman problem is a disproved conjecture on absolute stability of
Answer: 1982