Apparatus and associated methods relate to high accuracy timestamp support by controlling a first phase relationship between an outbound signal transmitted by a transmitting circuit and a local reference clock signal, measuring a second phase difference between a received data signal and the local reference signal, and measuring a third phase difference between a received time of day (RXTOD) signal and the local reference signal. In an illustrative example, a state machine circuit may be operated to control the first phase relationship, a phase measuring circuit may be configured to measure the second phase difference and the third phase difference. By comparing results obtained from phase control and phase measurement, the time of day (TOD) of each transmitted/received bit can be calculated at 1-bit level accuracy and achieve 1-bit level accuracy in the timestamp.
