VMS Help SET, DAY, Examples  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    1.$ SET DAY/PRIMARY

      The SET DAY command in this example overrides the current
      default day type and sets today until midnight to a primary
      day.

    2.$ SET DAY/DEFAULT

      The SET DAY command in this example overrides the previous
      SET DAY command and sets today's day type to the UAF-defined
      default.