As I previously mentioned, my Ubuntu web server seems to have a clock problem, presumably because it is running within VMWare. I found a simple way to keep the clock relatively accurate. This is probably not the best solution, but it works for me.
I created the following script within the directory /etc/cron.daily
ntpdate pool.ntp.org > /dev/null
Then I made it executable by issuing this command:
chmod +x filename.sh (change filename.sh to the name you gave to the script)
This syncronizes the system clock with an Internet time server every day. By the end of the day the time is off a minute or two, but accurate enough for my use.