Debian system clock unexpected change to wrong time
My setup and setting:
WinXP + VirtualBox + Guest OS (Debian Linux 6)
In my BIOS, CMOS clock sets to local time, which used by WinXP.
VirtualBox virtual machine set HW clock not UTC
In Debian, in /etc/default/rcS, UTC=no and /etc/timezone has "America/Los_Angeles" which is my location.
NTP service is turned off.
type date command I got:
Wed Mar 21 00:51:36 PDT 2012
that is 1 hour ahead of my real time. Then I run "ntpdate pool.ntp.org" and got:
20 Mar 23:52:17 ntpdate: step time server 126.96.36.199 offset -3570.239483 sec
that is correct time for me. Then I keep typing date to print current system, it shows correct time for a few seconds and then shows
Wed Mar 21 00:52:00 PDT 2012
Mysteriously the system time get changed back to the wrong time. I right away type "hwclock" to display HW clock, it shows:
Tue 20 Mar 2012 11:52:03 PM PDT -0.322598 seconds
that is the correct time set in BIOS.
So the issue here is that some software update the system clock after I set it to correct value manually. And I don't know what SW does that. And how come it's always 1 hour ahead of real time? Does it caused by day light saving? How to fix this?
Thanks in advance!