The association of timestamps with various data items is fundamental to the management of time-varying information because it has a pervasive effect on most aspects of a data model. Using intervals in timestamps, as do most data models, leaves a data model with a variety of choices for giving a meaning to timestamps. Specifically, some data models claim to be point-based while other data models claim to be interval-based. The precise definition of these properties is often confused. We argue that these properties can (and in fact should) coexist. Together they provide a powerful tool to define temporal operators that support advanced attribute semantics.