readclock - read the AT's real time clock
Readclock reads the AT's real time clock and sets the machine's time. It
is usually the second thing done in /etc/rc, the first thing is setting
the time zone by sourcing /etc/profile. This means that the clock is
assumed to tell the wall clock time. If you want to run the clock in GMT
then you can put TZ=GMT (or any other TZ value) in front of the readclock
-n Play-act, don't set the time nor change the calibration data, just
show what would be done.
-w Write the current time to the CMOS clock. Dangerous, see BUGS.
Don't forget to use TZ=GMT in front of readclock if the clock should
run in GMT.
-W Like -w, but also sets the status registers of the CMOS clock to
their proper values. (For if the clock suddenly runs at an odd pace
or has stopped and the BIOS doesn't repair it.)
-2, Add 20 to any year before 2000. If your CMOS clock year can't run
past 2000, then you can set it to 1980 and use -2 to correct the
year. Together with -w the year minus 20 is written to the clock.
/etc/profile Timezone and other shell initialization code.
Reported to not work on some AT's.
May mess up the clock royally when setting it (-w). Only if you have a
very standard AT and you are not afraid of having your CMOS setup reset
to the default with a "checksum error" should you use readclock to set
the time of the CMOS clock. You have been warned.
Kees J. Bot (email@example.com)