INT 1aH 04H: Read Date from Real-Time Clock

                                                                        [AT]
 Expects: AH    04H
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 Returns: AH    0
          CH    century, in BCD▲ (19H ... 20H)
          CL    year, in BCD     (00H ... 99H)
          DH    month, in BCD    (i.e., 01H=Jan ... 12H=Dec)
          DL    day, in BCD      (00H ... 31H)
          CF    NC (0) clock operating
                CY (1) clock not operating or busy being updated
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    Info: Obtains the current date from the battery-backed CMOS Real-Time
          Clock.

          Return values are in BCD▲; for instance, CX = 1998H = 1998.

          The BIOS avoids reentrancy by not returning the date if the clock
          happens to be in the process of being updated.  Thus, if CF is
          set on return, you should try a few more times before giving up.

See Also: INT 1aH (BIOS Time I/O)
          DOS fn 2aH (get system date)
          ROM-BIOS Functions
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