Technologies for high-precision timestamping of data packets is disclosed. Several sources of errors that may arise when timestamping the arrival or sending of data packets may be determined and corrected, including variable latencies, semi-static latencies, and fixed latencies. In the illustrative embodiment, a variable latency may arise due to a phase difference between a clock of a network interface card and a system clock. When a trigger pattern is detected, such as the start of a data packet, a trigger may be sent from a circuit synchronized to the clock of the network interface card to a circuit synchronized to the system clock. The phase difference between the edge of the clock on the network interface card and the edge of the clock of the system clock leads to an error in the timestamp value. Determining the phase difference allows for the error in the timestamp value to be corrected.