How Accurate is Your Computer Clock?
Sunday June 21, 2009
Some of you probably use NTP (Network Time Protocol) to keep your computer (and router) clocks synchronized to the correct time of day. NTP is a great technology, as left on their own the clocks on computers tend to drift and be inaccurate.
→ See also - What is the NTP Pool Project?
If your network uses NTP, its computers should be able to set their clocks within a few milliseconds of official time according to research studies. That's plenty accurate enough for most people. If you don't use NTP, consider setting it up (but you'll no longer have an excuse to be late for appointments!) On Windows PCs, simply look for the Internet Time tab under Control Panel "Date and Time."
→ More - Network Time Synchronization Research Project (udel.edu)→ See also - What is the NTP Pool Project?
Karen’s Power Tools, has a clock sync program on there that works very well. And free!
http://www.karenware.com/powertools/ptsync.asp
Since the default windows ntp time-server isn’t all that great, I set all the computers on our networks to update from pool.ntp.org.
Also, since NTP is implemented via UDP over port 123, you have to make sure that your router or firewall don’t block this. I’ve seen a good number of corporate and educational firewall implementations that neglect to make a rule to allow NTP traffic over 123! If this happens, then there is a strong possibility that computers on the network behind that firewall will be out of time sync. This will in turn adversely affect file syncronization over the network.
Qlock
http://www.qlock.com/