I want to put a survey/questionnaire right here: check real or fake. I suspect you know the answer. If a bug is never exercised, is it still a bug? For the philosopher examining the tree question and pondering observation and the knowledge of reality, there's a lot to think about. For a developer, the answer is a more clear cut "yes". It's still a bug. It still makes a noise. Not only if it's outside 9 to 5 (that's why we have support and cell phones), but even when it's that hour twice a year during the daylight savings switch. That's partially what test driven development is all about. And it's certainly the impetus behind making sure you catch all those edge cases, even if automating them means staring at your machine while it grinds through code contracts and Pex, speaking from a .NET perspective. I think the Microsoft Research description of what Pex does is great, "Pex finds interesting input-output values of your methods."
Title: If only we could say the same about ourselves.
Snarky: No, it's not a bug. That code only has to work from 9 to 5.