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

       /SINCE=time

    Input File-Selection Qualifier

    Selects files dated equal to or later than the specified date
    and time. You can enter the time in either absolute time or delta
    time. Specify these time values according to the rules described
    in the OpenVMS User's Manual. You can also specify the time using
    one of the following options:

    BACKUP     The BACKUP/RECORD operation (available only on Files-
               11 Structure Levels 2 and 5 volumes)
    TODAY      The current day, month, and year at 00:00:00.0 o'clock
    TOMORROW   24 hours after midnight last night
    YESTERDAY  24 hours before midnight last night