Sure, in theory the string 20xx-12-31T23:59:59 should never be created. But if it is created, so what? A time span is off by a second, in the positive direction

Sure, in theory the string 20xx-12-31T23:59:59 should never be created. But if it is created, so what? A time span is off by a second, in the positive direction. Not good, but shrug. I'm not saying it's a good thing. At time recording it's like the computer froze for a second. Compare this to the problem of there being a unix timestamp integer that refers to two different times, which is what naive positive leap second implementations resulted in. Real time spans being impossibly negative. Positive leap seconds are orders of magnitude worse. Unless you're writing time keeping software, negative leap seconds can be ignored and will be "just fine". And if you are writing time keeping or benchmarking software, then this is just another thing to not have a misconception about. > Generally UNIX time -> UTC conversion is considered to be infallible And generally there's two seconds between N and N+2.