I don't really understand why this is working even to the extent that is currently working. IIUC,local is supposed to return something like the number of seconds since 1970-01-01T00:00in local time (assuming that local time is an idealized calendar), but now we have a situation where in the failure cases, it just returns whatever the input was, and none of the callers have been updated to understand this. Why is thelocal` call required at all?

I suspect that this is not the right way to handle this. I don't fully understand what's going on here, but I think we either need to relax the validation inutc_to_seconds to allow forintermediate values to fall outsideMIN_YEAR/MAX_YEAR, or we need to find a way to do these same calculations that doesn't involve calculating these UTC seconds at all (or, if that's much slower than what we're doing now, try the current method and fall back to the slower method if we fall outside the boundaries during the intermediate values).