VMS Help SHOW, CLUSTER, Qualifiers, /BEGINNING  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /BEGINNING=time

    Specifies the time that the SHOW CLUSTER session is to begin. You
    can specify absolute time, a delta time, or a combination of the
    two. Observe the syntax rules for time values described in the
    OpenVMS User's Manual or the online help topic DCL_Tips (subtopic
    Date_Time).

    If you specify a future time, your process is placed in a state
    of hibernation until the specified time. Use this qualifier with
    the /OUTPUT and /ENDING qualifiers to run SHOW CLUSTER without
    direct user intervention.

    You can specify time as absolute time expressed as
    [dd-mmm-yyyy[:]] [hh:mm:ss.cc], or a delta time expressed as
    [dddd-][hh:mm:ss.cc], or a combination of the two. Observe the
    syntax rules for time values described in the OpenVMS User's
    Manual or the online help topic DCL_Tips (subtopic Date_Time).