In this joint talk, NextNav and Oscilloquartz will demonstrate results from lab and field work showing how 5G based terrestrial Positioning, Navigation, and Timing (PNT) signals can be used as a time source for network synchronization. This 5G terrestrial solution operates at 900 MHz to broadcast a 5G standard Positioning Reference Signal (PRS) which provides an accurate timing signal to provide resilient PNT services when GPS is unavailable. The session will show how PPS/TOD outputs from a NextNav timing receiver connect into a timing grandmaster and show system performance using standard timing metrics. We will present results with timing accuracy in the tens of nanoseconds range, traceable to UTC, and stable operation in both indoor and outdoor GNSS-denied cases. The talk will highlight what worked well, what calibration was required, and the key challenges. The focus will be on practical lessons and why adding terrestrial PNT as another source makes sense for building more resilient sync networks