Andy Lester gives out some excellent advice in Help save the endangered time servers. If you haven’t configured your computer to use pool.ntp.org, it’s well worth doing so. It will mean that your computer has a much better notion of what the time is.
On a related note, I was immensely pleased to see that Windows XP finally came with an NTP client when I got given a new PC at work last year. So now windows users can trust their clock as well.