INT 1Ah,  04h (4)        Read Real-Time Clock Date                       many

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

On entry:      AH         04h

Returns:       CF         Set if clock not operating; else cleared
CH         Century (19 or 20) (BCD)
CL         Year (BCD)
DH         Month (BCD)
DL         Day (BCD)


Notes:         All dates are in Binary Coded Decimal (BCD). For
example, November 15, 1987 will be reported as CX =
1987; DX = 1115.

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 information returned from this service could
differ from the system date. This is because the
real-time clock is read once upon system startup,
updating the system timer. All other references to
date use the system timer. If either the real-time
clock date is changed (via Service 05h) or the
system timer is changed (via Service 01h), the other
date is not changed accordingly.

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

See also: INT 1Ah, 05h
See also: INT 1Ah, 0Ah

INT 1Ah, 04h (4) Read Real-Time Clock Date many