BLINKER DEMONSTRATION DATE
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  Purpose : Specify expiration date for demonstration version

  Syntax  : BLINKER DEMONSTRATION DATE <yyyy/mm/dd>

  Example :   # Set the program expiration date

              BLINKER DEMONSTRATION DATE 1992/12/31


  This command is used to set the expiration date of a program, after
  which it will end with the "demonstration date limit exceeded" message.
  It may be set to any date in the format yyyy/mm/dd.

  This can be used to create a demonstration version of the program
  without having to modify the source code.  When the overlay manager
  loads overlays after the expiration date (as determined by the DOS
  system date), the error handling procedure BLERRPRG is called with error
  number 1208, indicating that the demonstration date limit has been
  exceeded.

  The source for this error handler is provided should you want to modify
  the text of the termination message.

  Note: the demonstration restrictions are only checked when overlays are
  called, so to use them please ensure that at least one function or
  procedure which is called regularly is overlaid.

  The function BLIDEMDTE() allows the limit to be extended from within the
  program. Please see the appropriate section in Chapter 7 for more
  details.