As services in telecommunications networks evolve and continue to require tight equipment time synchronization that is driven mainly by mobile LTE-A technologies and the further evolution to 5G, operators are starting to look at ways to distribute absolute time of day information in their networks. While different options exist, it is natural to question if the transport network can be leveraged for such a purpose because it is part of the common, pervasive and low-level infrastructure and is already used for frequency transport. Yet, while the final answer to this question is yes, thinking that because the optical transport network/wavelength division multiplexing (OTN/WDM) technology is by design transparent to frequency and that it will be transparent to phase and time of day as well, is a naïve approach that utterly fails. This white paper explains the need for phase and time of day alignment, the underlying challenges in providing a synchronization as a service over the transport network, and the available solutions provided by the Nokia 1830 Photonic Service Switch (PSS) family.