In this paper, we investigate the relationship between two decidable interval-based temporal description logics that have been proposed in the literature, T L-ALCF and ALCF. Although many aspects of these two logics are quite similar, the two logics suggest two rather different paradigms for representing temporal conceptual knowledge. In this paper, we exhibit a reduction from T L-ALCF concepts to ALCF concepts that serves two purposes: first, it nicely illustrates the relationship between the two knowledge representation paradigms; and second, it (...) provides a tight PSPACE upper bound for T L-ALCF concept satisfiabiliy, whose complexity was previously unknown. (shrink)