What marks the moment of scientific discovery? This paper examines how this moment is determined, and the extent to which it involves conventional elements. Although scientific practice often treats discovery as a discrete event, philosophical accounts reveal its conceptual and temporal complexity. I begin with Kuhn’s distinction between that- and what-discoveries, as well as Schindler’s refinements. In order to address the question of when a discovery occurs, I draw on the recent Change-Driver account of scientific discovery by Dürr and Mills, integrating a more nuanced theory of scientific problems. Building on Nickles’ constraint-inclusion model of scientific problems, I argue that the moment of discovery is shaped by the evolving structure of problems and the conventions that guide their resolution. This approach highlights the pragmatic and often negotiated nature of claims to discovery, offering a more adequate account of how discoveries are recognised and situated in time within scientific practice. The account is illustrated through the case of the Higgs boson, where theoretical expectations, empirical data, and institutional decisions jointly shaped when the discovery was declared.