It is generally agreed that as a fundamental feature of the world, time merits treatment within an upper ontology, that is, an ontology that is designed to capture those categories which are sufficiently generic to transcend the specific subject matters of any particular domain ontologies. In this paper I examine how time is handled within three well-known upper ontologies (BFO, DOLCE, and GFO), and follow this with a discussion of three key issues emerging from the survey, namely dimensionality (the treatment of instants and intervals), frame-dependence (as required by the Theory of Relativity), and indexicality (the status of past, present and future). The overall conclusion is that while existing upper ontologies tend to adopt some kind of compromise between a supposedly objective, scientific account of physical time, and a more subjective, cognitive account of time as we experience it, the fundamental philosophical and scientific questions concerning the nature of time have scarcely been addressed by any of them.