Related to human activities, there are two aspects of the world: One is the observed world (epistemology) and the other is the existed world (ontology). This article discusses the nature of time and space from the epistemological and the ontological aspects. From the epistemology angle, time and space are relative (observed). From the ontology angle, time and space are absolute (existed) and the universe is a timeless world, which means that all the past, the present and the future exist eternally. [Nature and Science 2003;1(1):1-11].