windows & linux time problem
 

Well I have linux (fedora 11) and XP in same machine and time is not same in this two os. When I correct time in XP, the time of linux change and when change time in linux, XP time change.
How can I solve this?

This is a common problem.

Windows sets the hardware clock to local time, and insists on doing so.

Linux traditionally uses the hardware clock set to UTC.

You need to configure Fedora so that it treats the hardware clock as set to local time. You should have been given this option at installation, but evidently it wasn't set right then.

A quick google reveals that running 'system-config-time' (probably as root) should sort things out.

You also want to make sure that only ONE of your OSes does the daylight saving time adjustments.

which time changes when
 

All that cantab says makes good sense in your situation. Also:

When you "change the time" you alter the information of the running operating environment.

The running operating environment grabs the hardware (BIOS) clock time at boot time. Where did this hardware clock learn the time?

When you "change the time" do you use the options that save that change to the hardware clock? If not, then as you re-boot, the OTHER environment learns the old hardware time not the current environment time. My Ubuntu Koala implements the hwclock --set --date=... command to alter the hardware clock setting.

Cheers,
~~~ 0;-Dan