The paper introduces the concept of virtual time, a new paradigm for organizing and synchronizing distributed systems. Virtual time provides a flexible abstraction of real time, similar to how virtual memory abstracts real memory. The Time Warp mechanism, a synchronization protocol, implements virtual time using lookahead-rollback and antimessages. Virtual time is applied to distributed discrete event simulation and distributed database concurrency control. The Time Warp mechanism ensures that processes execute without regard to synchronization conflicts, rolling back processes to a previous time if conflicts are detected. The paper compares virtual time to other synchronization mechanisms, such as Lamport's work, Reed's pseudotime, and Schneider's synchronization protocols. The Time Warp mechanism is described in detail, including its local and global control mechanisms, and examples of its application in distributed systems are provided.The paper introduces the concept of virtual time, a new paradigm for organizing and synchronizing distributed systems. Virtual time provides a flexible abstraction of real time, similar to how virtual memory abstracts real memory. The Time Warp mechanism, a synchronization protocol, implements virtual time using lookahead-rollback and antimessages. Virtual time is applied to distributed discrete event simulation and distributed database concurrency control. The Time Warp mechanism ensures that processes execute without regard to synchronization conflicts, rolling back processes to a previous time if conflicts are detected. The paper compares virtual time to other synchronization mechanisms, such as Lamport's work, Reed's pseudotime, and Schneider's synchronization protocols. The Time Warp mechanism is described in detail, including its local and global control mechanisms, and examples of its application in distributed systems are provided.