File is Not a Calendar Datafile

  DECwindows Calendar opened the file you specified, but the
  file is not a Calendar datafile.

  If you are using the logical name DECW$CALENDAR_
  FILE, make sure that it is pointing to a valid DECwindows

  Calendar datafile.  If this logical is not defined, Calendar uses
  SYS$LOGIN:DECW$CALENDAR_FILE.DWC as the default
  datafile.