From the article:
Consider an example. Suppose that the clock on campus (which keeps accurate time and is well maintained) stopped working at 11:56pm last night, and has yet to be repaired. On my way to my noon class, exactly twelve hours later, I glance at the clock and form the belief that the time is 11:56. My belief is true, of course, since the time is indeed 11:56. And my belief is justified, as I have no reason to doubt that the clock is working, and I cannot be blamed for basing beliefs about the time on what the clock says. Nonetheless, it seems evident that I do not know that the time is 11:56. After all, if I had walked past the clock a bit earlier or a bit later, I would have ended up with a false belief rather than a true one.
Why do I not know that the time is 11:56? As stated, (1) it is true, (2) I believe it to be true and (3) I am justified in believing that it is true. Getting to class just in time provides me we further evidence that the time was in fact 11:56 when I passed the clock.
If I had passed by a little earlier or a little later I would be early or late for class so my belief would not cohere with facts around me. That would lead to a conflict between my belief and the truth, and I would have to question the justification for my belief.
Let’s suppose that the clock gets repaired without me knowing it. Then I never have a reason to question my belief at the time I glanced at the clock. On the other hand, if I see the clock getting repaired or later get told that it was broken, then, again, the justification for my belief falls apart.
So, as far as I’m concerned, in the example above I have a justified true belief, hence knowledge. As it so happens, it is purely circumstantial that I have a justified true belief. But this particular JTB has been seasoned with that wonderful philosophical spice called “luck” or “fluke”.