Int 1Ah, 02h            Read Real-Time Clock Time                        many

    Reads the time from the computer's real-time clock.

        Entry   AH = 02h

        Return  CF   Set if clock not operating; else cleared
                CH = Hours (BCD)
                CL = Minutes (BCD)
                DH = Seconds (BCD)
                DL = 1 if daylight saving time option; else 0

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    All times are in Binary Coded Decimal (BCD). For example, 9:04.12
    am will be reported as CX = 0904; DH = 12.

    The real-time clock is the clock that runs even when the computer
    is turned off. A CMOS battery is used so that, even while the
    computer is off, the date, time, and alarm time are maintained.

    This service is available only for ATs, XT-286s, and PC
    Convertibles. Previous machines will report unpredictable results
    (including the state of the Carry Flag).

    The daylight saving time option is not reported on ATs with dates
    prior to 6/10/85.

    The information returned from this service could differ from the
    system time. This is because the real-time clock is read once upon
    system startup, updating the system timer. All other references to
    time use the system timer. If either the real-time clock is
    changed (via Service 03h) or the system timer is changed (via
    Service 01h), the other clock is not changed accordingly.

    Even though the system uses the system timer for timing
    information, both the real-time clock and the system timer are
    updated continuously.