The issue of temporal reasoning in an online real-time expert system in the field of process control is addressed. An alarm filtering problem is described, and the integration of a point-based time map manager (TMM) with an inference engine, to manage the temporal constraints, is proposed. The TMM manages only imprecise future time points and must comply with the constant modification of the current time and thus with the removal of time points that are moved to the past. Temporal restrictions in the left-hand sides of rules are also described, together with the need for management of pending queries that may receive an answer when the uncertainty pervading the future is reduced.>