With increasing use of computing systems while on the move and in constantly changing conditions, whether it is via mobile devices, wearable computers or embedded systems in the environment, time plays an increasingly important role in interaction. The way in which information is represented in an interface is fundamental to interaction with it, and how the information is used in the users tasks and activities. Dynamic representations where the user must perceive changes in the information displayed over time pose a further challenge to the designer. Very often this information is integrated with information from the environment in the performance of the user's tasks. The diminutive size and limited display capabilities of many ubiquitous and mobile computing devices further motivate careful design of these displays. In this paper we look at how time can be taken into account when reasoning about representational issues from the early stages of design. We look at a model which can be used to reason about these issues in a structured fashion, and apply it to an example.