 Neither Prior’s nor Reichenbach’s frameworks can account for the difference between, for instance, the simple past (“I wrote a letter”) and the past progressive (“I was writing a letter”). The relevant distinction here is one of aspect rather than of tense and naturally requires an interval-based or event-based setting to be adequately dealt with. For accounts along these lines, see e.g. Dowty (1979); Parsons (1980); Galton (1984); and van Lambalgen and Hamm (2005).