In some embodiments, an apparatus and a system, as well as a method and an article, may operate to receive a derived clock signal downhole, the derived clock signal being derived from a surface clock signal (associated with a surface clock), such that the frequency of the derived clock signal is less than the frequency of the surface clock signal. Further activity may include measuring the frequency of the derived clock signal in terms of an uncorrected downhole clock frequency (associated with a downhole clock) to provide a measured frequency equivalent, and correcting time measurements made using the downhole clock, based on the measured frequency equivalent, or based on an actual frequency of the downhole clock determined according to the measured frequency equivalent. Additional apparatus, systems, and methods are described.