Recommendation ITU-T G.8272.1 specifies the requirements for enhanced primary reference time clocks (ePRTCs) suitable for time and phase synchronization in packet networks. It defines the error allowed at the time output of the ePRTC. These requirements apply under the normal environmental conditions specified for the equipment. Amendment 1 to Recommendation ITU-T G.8272.1 (2024/01) provides the following updates: Changed “time standard” to “time scale” and clarified the use of UTC. Replaced the term “calibration” with the more appropriate term “compensation”. Added new clause 8.3 on recovery from holdover. Added new clause 9.1.1 on input phase and time interfaces. Added synchronous Ethernet as an optional new input frequency interface. Added new Appendix VI on ePRTC used as a travelling clock. Added material on “UTC time signal source” to clause 5 Conventions.