A transparent clock adaptor is provided for use with a router, switch or other network device that does not otherwise support transparent clock functionality. The transparent clock adaptor comprises a network port for coupling to a link of a network, a local port for coupling to a port of the network device, transparent clock processing circuitry operative to perform one or more transparent clock timing adjustment operations for each of a plurality of packets including at least one packet arriving in the adaptor via the network port and at least one packet arriving in the adaptor via the local port, and a synchronization interface for communicating with a corresponding synchronization interface of at least one other transparent clock adaptor. The adaptor can operate both as an ingress adaptor for packets arriving over the network link for delivery to the network device and as an egress adaptor for packets arriving from the network device for delivery over the network link.