INT 1aH 03H: Set Time on Real-Time Clock

                                                                        [AT]
 Expects: AH    03H
          CH    hours, in BCD▲
          CL    minutes, in BCD
          DH    seconds, in BCD
          DL    00h = no Daylight Savings Time option
                01h = Daylight Savings Time option
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 Returns: AH    0
          AL    value written to CMOS 0bH register
          CF    NC (0) clock operating
                CY (1) clock not operating or busy being updated
          ──────────────────────────────────────────────────────────────────
    Info: Sets the time for the battery-backed CMOS Real-Time Clock.

          All input values are in BCD▲ in 24-hour format; for instance,
          CX = 1234H = 12:34pm.

          The BIOS avoids reentrancy by not allowing the time to be set 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 2dH (set system time)
          ROM-BIOS Functions
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