Aggressive timed circuits, including synchronous and asynchronous self-resetting circuits, are particularly challenging to design and verify due to complicated timing constraints that must hold to ensure correct operation. Identifying a small, sufficient, and easily verifiable set of relative timing constraints simplifies both design and verification. However, the manual identification of these constraints is a complex and error-prone process. This paper presents the first systematic algorithm to generate and optimize relative timing constraints sufficient to guarantee correctness. The algorithm has been implemented in our RTCG tool and has been applied to several real-life circuits. In all cases, the tool successfully generates a sufficient set of easily verifiable relative timing constraints. Moreover, the generated constraint sets are the same size or smaller than that of the hand-optimized constraints.