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

 Expects: AH    04H
 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
    Info: Obtains the current date from the battery-backed CMOS Real-Time

          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