Researchs on environmental devices have shown the key place of negotiation in the elaboration of environmental rules. These negotiations bring together actors with different knowledge of natural environment and various relationships to time. This article aims at studying the articulation of these different relationships to time within negotiations. Founded on the notion of “regimes of historicity” developed by F. Hartog (2003), the analysis shows how knowledge relying on past experience or developing anticipations of dangers articulate in negotiations to construct a relationship to time as a frame of reference for the actors. This frame of reference which establishes inequalities amongst the knowledge of the different actors is the product of processes of marginalization, exclusion and translation that deserve attention. The resulting relationship to natural environment is analyzed with reference to the place given to uncertainty in knowledge and in implementation of management schemes. The negotiations on which this article is based concern the creation of a protected area and the restoration of water quality in Brittany.