如何修改linux 系统时间，CentOS系统

[root@canary-12-06 sbin]# echo "xen.independent_wallclock = 1" >> /etc/sysctl.conf

[root@canary-12-06 sbin]# ./sysctl -p
net.ipv4.ip_forward = 0
net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.default.accept_source_route = 0
kernel.sysrq = 0
kernel.core_uses_pid = 1
net.ipv4.tcp_syncookies = 1
kernel.msgmnb = 65536
kernel.msgmax = 65536
kernel.shmmax = 68719476736
kernel.shmall = 4294967296
error: "Invalid argument" setting key "xen.independent_wallclock"
error: "Invalid argument" setting key "xen.independent_wallclock"
xen.independent_wallclock = 1

[root@canary-12-06 sbin]# date -s 13:30:00
Tue Jan 14 13:30:00 CST 2014
[root@canary-12-06 sbin]# date
Tue Jan 14 13:30:03 CST 2014