Researchers have advocated that the acquisition of user preferences is important to the successful adoption of electronic negotiation systems. In this paper, we focus on one such preference, namely time preference, wherein the price of a good/service varies according to the delivery/consumption time. Time preference is a behavioral aspect that varies across buyers. We discuss how different types of preferences can be elicited, represented and integrated with electronic negotiations. We discuss three experiments to study the effect of time preferences on negotiation. The first is a preference elicitation experiment involving 36 subjects. The next two are agent-to-agent negotiation experiments, one based on the individual preferences obtained earlier and the other based on an expanded dataset on both individual preferences as well as negotiation parameters. The agent-based experiment compares outcomes and efficiencies between the standard exponential discounting model and two behavioral models of time preference. Our results bring out the preferences of subjects, as well as the extent to which negotiation is affected and enhanced by the incorporation of time-preferences.