Sync date on linux

yum install ntp

Run this to sync the date..

/usr/sbin/ntpdate -s -u 129.132.2.21

Sync the hardware clock..

hwclock --systohc


Run from cron..

0 */6 * * * /usr/sbin/ntpdate -s -u 129.132.2.21
1 2 * * * hwclock --systohc