Temporal adverbial phrases such as recently and some time ago have a special function in communication and temporal cognition. These adverbials are deictic, in that their meaning is tied to their time of utterance; and they are vague, in that the time periods to which they apply are under-specified in comparison to expressions such as yesterday, which precisely indicates the day before the day of utterance. Despite their vagueness, conversational participants have a mental image of when events described using these adverbials take place. We present a study that aims to quantify this mental model in terms of fuzzy or graded membership. To achieve this, we investigated the four English temporal adverbials recently, just, some time ago and long time ago as applied to types of events with different durations and frequencies, by conducting surveys to measure how speakers judge the different adverbials to apply in different time ranges. Our results suggest that it is possible to represent the meanings of deictic vague temporal adverbials geometrically in terms of graded membership within a temporal conceptual space.