Though unity of time is by no means a necessary element to digital storytelling, confining actions to a specified period of time, such as a day, a week, a lifetime or a particular era in history gives the audience something by which they can orient themselves in a story and sets up certain expectations.
If the audience is aware that a story is going to cover the lifetime of a particular individual, then the audience can freely travel back and forth through that lifetime, since it is understood that certain sorts of things tend to happen at certain times in a person's life, and what the audience is relishing is how this individual uniquely passes through our common human experience.
When dealing with a story that covers a particular era, storytellers can rely on some common cultural knowledge to suggest causal links, as well as genre expectations from how that period has regularly been portrayed in other stories. MUDs often use these common understandings to build up their story worlds.
More arbitrary lengths of time can become problematic when not combined with other unities. The movie Night on Earth [Jar91] is about a single night, but five different cities. The other unity which holds this together as a single story is that all of the events take place in the same metaphorical space of the taxi. This technique can easily be used in a digitally based work.
Copyright 1999 Katherine Phelps