VMS Help DTM, SHOW, HISTORY, Command Qualifiers, /BEFORE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

   /BEFORE=time

   Lists all history information prior to a specified date. The time
   is the current date and time, and the information displayed is
   whatever was logged prior to the SHOW HISTORY command. The time
   value can be an absolute, delta, or combination time value, or
   one of the following keywords: TODAY, TOMORROW, or YESTERDAY.