Understanding the importance of accurate time

Accurate timekeeping on computers wasn't always real important. My very first computer job involved working with a pair of transistorized computers that were each the size of a refrigerator, and that had orders of magnitude less processing power than a modern smartphone. There was no hardware clock, and there was no NTP. Every time we rebooted these beasts, we just looked at our notoriously inaccurate wall clock and manually entered the time from it. Things didn't change much with the early personal computers. I mean, you still had to set the time manually, but they did eventually come with battery-powered hardware clocks that would still keep time when you shut the computers down.

Nowadays, it's critically important for computers to maintain accurate time. Scientific computing, log keeping, database updating, and financial transactions all require it. Certain security protocols, such as Kerberos, DNSSEC, and Transport...