According to an aspect, there is an apparatus comprising at least one processor and at least one memory including computer program code. The at least one memory and the computer program code configured, with the at least one processor, to cause the apparatus at least to receive, from a serving access node, a downlink radio resource control message comprising reference time information for a clock provided by the serving access node and traceability information for enabling traceability of the clock to a reference time standard. The traceability information comprises at least information on a clock class indicative of a current status of the clock provided by the serving access node.