Fixed date time not synchronize permanently in Linux

Use cront for send command ntpdate every minute and store log in /tmp/ntpdate.log:
1-CentOS
login as root
  #yum install ntpdate
  #touch /tmp/ntpdate.log   (root owner)
  #crontab -e
  Add this line to send command ntpdate every minute and keep log to /tmp/ntpdate.log

* * * * * /sbin/ntpdate 0.centos.pool.ntp.org>>/tmp/ntpdate.log

2-Debian
      login as root
      #yum install ntpdate
      #touch /tmp/ntpdate.log   (root owner) 
      #vim /etc/crontab
      Add this:

* * * * * root /usr/sbin/ntpdate 0.pool.ntp.org >> /tmp/ntpdate.log