William Delbert Gann (June 6, 1878 – June 18, 1955) or WD Gann, was a finance trader who developed the technical analysis methods like the Gann angles and the Master Charts, where the latter is a collective name for his various tools like the Spiral Chart (also called the Square of Nine), the Hexagon Chart, and the Circle of 360. Gann market forecasting methods are purportedly based on geometry, astronomy, astrology, and ancient mathematics. Opinions are sharply divided on the value and relevance of his work. Gann authored a number of books and courses on shares and commodities trading.