There is a need to keep your computer clock accurate for some of the digital modes. There are several ways hams have been trying do do this ands some have become outmoded with the newer Windows operating systems. Meinberg NTP for Windows is the way to go. It is free and it is also the "official" Network Time Protocol client software. The only downside to ham software needing this level of accurace is that it probably would not be a good mode in an emergency. There would be no to keep the clocks that accurate without using a GPS signal or something else. How many Hams would be prepared for that? Julian, G4ILO has a good write up about this on his Blog. Check it out and see if you can keep up with time.