We describe DISTIL (DIstributed design of SpaTIo-temporaL data), a web-based conceptual modeling prototype system that can help capture the semantics of spatio-temporal data. Via DISTIL, we describe an annotation- based approach that divides spatio-temporal conceptual design into two steps: first capture the current reality of an application using a conventional conceptual model without considering the spatial aspects, and only then annotate the schema with the spatio-temporal semantics of the application. A database development team can use DISTIL to capture and validate their spatio- temporal data requirements. Using DISTIL we demonstrate that the annotation- based approach for capturing spatio-temporal requirements is straightforward to implement, satisfies ontology-based and cognition-based requirements, and integrates seamlessly into the existing database design methodologies.