Library /sys$common/syshlp/mailhelp.hlb DIRECTORY, Qualifiers, /SINCE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /SINCE=date

    Selects mail messages received on or after the specified date.
    The format for the date is dd-mmm-yyyy. If you do not specify a
    date, Mail displays a listing of all the mail messages received
    on the current day. You can also specify the keywords YESTERDAY
    and TODAY. For example, the command DIRECTORY/SINCE=YESTERDAY
    would give you a listing of all mail messages received since
    yesterday.