Who canonized Saint Daniel the prophet?

Ancient saints were not canonized as the process for canonization was not instituted until about the 12th century. The person would have been declared a saint, usually by a local bishop, based on their life and merits. Martyrdom was an almost automatic assurance of being declared a saint. Today, only the pope can declare a person to be a saint after years of investigating by the Sacred Congregation for the Causes of Saints. The Church does not really make saints. Only God can do that. The role of the canonization process is to assure that the person is really in heaven and would be a person worthy of emmulation. As to Old Testament personages, they are usually not accorded the title of saint. That is usually referred to individuals who entered heaven after the birth of Our Lord. That is not to say that they are not saints, they are generally not given the title.