Time synchronization in Cognitive Radio Networks (CRNs) is a demanding task due to the dynamic and cooperative nature of these networks. DCR-Sync, a novel time synchronization protocol for CRNs is proposed. DCR-Sync is fully distributed and resilient towards failure of root nodes, i.e., the nodes which play the role of master on the synchronization process. The authors present DCR-Sync in two versions. The first version is static in nature, and the second version can adapt dynamically to network changes. This protocol aims to be distributed and reliable even in root node failure. DCR-Sync following two versions, called DCRSync1 and DCR-Sync2.