The aim of the present work is to introduce a pattern-based method for assisting the user during the temporal Requirement Specification (RS) phase. Indeed, since the user usually has to handle abstract notation as well as mathematical-based languages within this phase, RS is becoming more and more tedious and error-prone especially when dealing with complex systems. The authors' method begins by defining a new typology while taking into account all the common temporal requirements one may meet when specifying a system. Then, a literal word-based formal grammar able to express all the types of the identified requirements has been developed. Actually, the goal is to assist the user during the requirement identification with some means that are simple, intuitive, albeit rigorous. Finally, a generic set of observation patterns relative to the new time constraint taxonomy is defined. In practice, to check a given temporal constraint, its relative observation pattern is instantiated to obtain an observer that will stand for a watchdog for the associated requirement on the system.