Episodic memory is composed of events

1. Friedman(1993) has reviewed episodic memory and his main finding is that episodic memory does not consist of a continuous trace, like a video tape recorder, but rather consists of a sequence of discrete records representing discrete events. Further, the relations among events are not necessarily those of temporal adjacency but of other general semantic relations. It seems that there are some temporal ordering relations however.

2. To quote Friedman: ``Memory for time is not built on special temporal codes or a chronologically organized memory store. Instead, our chronological sense of the past is the product of an ongoing constructive process in which we draw on, interpret, and integrate information from:
1. our stored knowledge of time patterns,
2. and general knowledge about time,
3. the contextual associations of particular memories,
4. order codes linking related events,
5. occasional direct associations between event and time names, and
6. rudimentary clues to the ages of memories.''
(my numbering)

3. Temporal indexing. The representation of events in autobiographical memory has been discussed by Lawrence Barsalou. His main conclusion was that the top level of indexing is based on time.

4. Rhythms and clocks. There could well be variables with diurnal and other rhythms which would be input to the hippocampal formation.