The ability to synchronize remote clocks is a surprisingly fundamental part of civilian and military infrastructure, from cell phone networks to power grids, onward to GPS and gravitational wave detection. Unfortunately, it is known that it is not hard to spoof a GPS signal and use it to steer a target clock to a desired time. Under non-adversarial conditions, time synchronization is a hard physics problem; when a malicious adversary is present, it becomes a task in secure metrology. I will present a protocol inspired by the techniques from quantum communication that allows extremely accurate and mostly-secure synchronization of two remote clocks in the presence of a well-equipped adversary. I will discuss the experimental implementation, the security implications, and the precision limits of the technique.