Well, it's time for the semi-annual daylight savings time change. One thing that has annoyed me in recent years is the fact that, for a few weeks after the time change, it seems that many clocks are out of sync -- some a few minutes fast, others a few minutes slow.
For networked computers, the Network Time Protocol (NTP) can be used to synchronize the system clock with time standards available on the Internet, which are in turn tied to atomic clocks operated by the National Research Council in Canada, the National Institute of Standards and Technology in the US, and other organizations. NTP used to be a chore to set up, but now it's pretty trivial -- in Fedora, for example, you just have to check the NTP option during installation (or select System>Administration>Date & Time, click on the Network Time Protocol tab, and then checkmark the field labeled "Enable Network Time Protocol").
What many people don't realize is that cell phone networks also use NTP (or a similar protocol, I'm not sure about the inner workings of the cell networks). This means that most cellphones display the time to within a second of the official standard -- it's like having an atomic time reference in your pocket.
So, if you're adjusting your clocks tonight, consider setting them according to your cellphone.