Days, are intervals, not points in time. Traditionally a day is the time from sunup to sundown, in modern contexts it usually goes from midnight to midnight. T

Days, are intervals, not points in time. Traditionally a day is the time from sunup to sundown, in modern contexts it usually goes from midnight to midnight. This is the question about timestamps, are the points in time, or are they second long intervals. I think the logical reading is the first. This opens up the question of "what the hell is the word inclusive doing there", I think the answer is it is being used to say "if you don't know whether you're inside or outside the interval, you are inside". If your clock runs on a 2 second interval, and you know it's somewhere between 9:59:59 and 10:00:01, when the certificate expires as 10:00:00, you take the inclusive definition and say "still valid" because otherwise you might be rejecting a valid certificate. It is perhaps also being used to say that "both ends of the interval aren't open". If I have on certificate that expires at 10am, and another that becomes valid at 10am, then there is no gap between there validity.