I have a VPS running on Cent Os 5.8 (x86). There are situations in which we are forced to reset the entire VPS (it hangs and the only way to get it back on is to reset it). When we do so, the time is reset too.
We use the following command to set the time (the timezone is configured through kloxo admin panel and is not reset like the time does):
#date +%T%p -s "10:10:10" (as for hour 10 and minutes 10 and seconds 10 ) You can use NTP (Network Time Protocol) if this machine is Internet connected. This will synchronize the machine's clock to an Internet time server.
yum install ntp, then edit the /etc/ntp.conf file so that you have at least one line that looks like:
server 0.pool.ntp.org Then chkconfig ntpd on so that it will start up automatically on boot.
Once this is done, start the NTP service with service ntpd start or /etc/init.d/ntpd start. Or, for newer versions of CentOS that use systemd, run systemctl start ntpd.
Here's some additional documentation from Slicehost.
The program date sets the system clock, i.e. the clock maintained internally by the operating system. There is a separate clock inside the computer which keeps the time when the computer is off (or rebooting). If you've set the system clock manually, call hwclock to set the hardware clock as well.
hwclock --utc --systohc (Replace --utc by --localtime if your hardware clock is set to local time. This should only be done if you dual boot with Windows.)
Some distributions have a script that calls hwclock with the right options (--utc or --localtime, and if relevant other hardware-specific options). For example, on Debian, run /etc/init.d/hwclock.sh stop. I don't know about CentOS.
All of this is for a one-time thing. If your computer has a permanent or frequent Internet connection, once you've set the time approximately right manually, make it synchronize its time over the network, using NTP. See cjc's answer.
