Function 2Bh (43)        Set System Date

    Sets the current system date.

       On entry:      AH         2Bh
                      CX         Year (1980 - 2099)
                      DH         Month (1 - 12)
                      DL         Day (1 - 31)

       Returns:       AL         00h      if valid date specified
                                 FFh      if invalid date specified

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       Note:          Note the similarity between the register setup for
                      this function, and the registers returned by
                      Function 2Ah, Get System Date.