While many techniques exist for detecting mechanical tampering in an integrated circuit supply-chain, estimating the time-of-occurrence of the tampering event has proven to be challenging. This work builds upon our previously demonstrated self-powered mechanical event detector and self-powered timing device to report a chip-scale system that can accurately time-stamp the occurrence of the tampering event. The proposed system uses a combination of Fowler-Nordheim tunneling for continuous time-keeping and a linear hot-electron injector for sensing and recording of mechanical events. Using devices fabricated in a 0.5 µ-m standard CMOS process, we demonstrate event time-stamping with an accuracy of 95% over a duration of 3 days. This accuracy can be further improved by incorporating a parametric model during the system calibration phase.