VMS Help SET, SECURITY, Qualifiers, /BEFORE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /BEFORE[=time]

    Selects only those files dated prior to the specified time.
    You can specify time as absolute time, as a combination of
    absolute and delta times, or as one of the following keywords:
    BOOT, LOGIN, TODAY (default), TOMORROW, or YESTERDAY. Specify
    the /CREATED or the /MODIFIED qualifier to indicate the time
    attribute to be used as the basis for selection. The /CREATED
    qualifier is the default.

    For complete information on specifying time values, refer to the
    OpenVMS User's Manual or the online help topic DCL_Tips (subtopic
    Date_Time).