In an era where distributed architectures, contested environments and precision timing are mission-critical, there is a growing need for resilient, GNSS-independent time transfer solutions. Time transfer systems are used to measure the time offset of a local clock to a distant reference, enabling clock synchronization or correction, correlated observations, and communications handoffs. The Aerospace Corporation’s Time Transfer Testbed addresses this need with a state-of-the-art capability for evaluating, emulating and validating time synchronization techniques across RF and optical links.