The basic hypothesis of the author is that under the influence of technological development and market pressure, situations take on temporal characteristics that are more and more difficult for the operator to control. The temporal strategies traditionally installed by the operator disappear, are transferred or transformed. Far from counterbalancing these phenomena, the displays, as they are designed in the workplace, obliterate the temporal dimension. The errors that are seen to appear are the product of a mismatch between the characteristics of the situation and the operator's resources. Four mechanisms of time estimation are discussed. Field study results on temporal strategies, such as anticipation, assessment of a process evolution and planning adjustment are developed.