I've seen this happen a few times. I haven't looked at the code in depth but I'm assuming it is due to conversion from a negative Celsius that gets rounded down.
Yes it happens because of rounding, though rounding is only done for display. Not a bug, and I do not care enough for it to change it.
(In reply to Harald Judt from comment #1) > Not a bug, and I do not care enough for it to change it. I beg to differ. It *is* a display bug since there is no such thing as -0. Whether you care or not about it and will fix it, is a different matter.
If you provide a patch that solves this for Fahrenheit only, attach it and reopen this bug report, and I will apply it.