We consider a classic Resource-Constrained Project Scheduling (RCPSP) problem which is known to be NP-hard. For defined project deadline T, each task of the project can be associated with its temporal domain - a time interval in which this task can be processed. In this research, we present new polynomial-time algorithms (propagators) used to tighten such temporal task domains in order to make the optimization problem easier to solve. Numerical experiments show the efficiency of developed propagators in preprocessing for improving the performances of existing solution methods for RCPSP. Moreover, we show how these propagators can be used for calculating an efficient lower bound on project makespan.