VMS Help SET, TIME, Description  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Resets the system clock, which is used as a timer to record
    intervals between various internal events and as a source clock
    for displaying the time of day.

                                   NOTE

       The SET TIME command will not work if there is a time
       service available on your system or OpenVMS Cluster.