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

       /SINCE[=time]

    Selects only those files dated on or after 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 one
    of the following qualifiers with the /SINCE qualifier to indicate
    the time attribute to be used as the basis for selection:
    /BACKUP, /CREATED (default), /EXPIRED, or /MODIFIED.

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