A data network node is configured for operation as a time-transfer boundary clock, and has at least one time-transfer slave network interface and several time-transfer master interfaces, all configured for operation according to a time-transfer protocol. The data network node also includes a clock source interface configured for connection to a synchronous clock source supplied from a remote node, as well as a real-time clock (RTC) circuit. The RTC circuit supplies time-of-day data for time-transfer messages sent via the second network port and selectively operates in a first mode, wherein the RTC frequency is driven by a clock signal from the clock source interface, a second mode, wherein the RTC frequency is driven by a clock signal derived from time-transfer messages received by the time-transfer slave interface, and a third mode, wherein the RTC frequency is driven by a local clock signal from local clock source.