In this paper, we present a novel technique for modeling, checking, and enforcing temporal constraints in workflow processes containing conditionally executed activities. Existing workflow time modeling proposals either do not discriminate between time constraints that apply to disparate execution paths, or they treat every execution path independently. Consequently, superfluous time constraint violations may be detected at modeling time, even when each execution path does not violate any constraints. In addition, scheduling conflicts during process execution may not be detected for activities that are common to multiple execution paths. Our approach addresses these problems by (partially) unfolding the workflow graph associated with a process that contains conditionally executed activities and, then, incorporating the temporal constraints in the time calculations performed on the unfolded graph.