Library /sys$common/syshlp/sysmanhelp.hlb SHUTDOWN, NODE, Qualifiers, /REBOOT_TIME  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /REBOOT_TIME=time

    The time when you expect to reboot the system such as
    IMMEDIATELY, IN 10 MINUTES, 2 P.M., or 14:00:00. Shutdown
    displays this time in a shutdown message to users.