I'm not sure this counts as a constructive comment, but an interesting anecdote anyway - an early coding partner of mine once wrote a procedure he expected to run once exactly every second by continuously polling the time in a while/do_nothing loop until exactly one second had passed. It took some convincing to get him to accept that try as he might, it was very unlikely that "==" was what he wanted there.

The best part was that this was in Javascript (and obviously he was not using a timeout). The entire page would lock up while it waited for the second to elapse. He never even figured out the obvious usability concern because he was so confounded by the fact that the procedure wasn't getting called after a second had passed.

Ok, to be fair, it was a freshman year programming class - not an unexpected or even unusual mistake. But it gave me a chuckle just now remembering it.