Hi, coreutils 8.29-1 on Arch Linux.
$ date -uIs -d @-62135596801 0000-12-31T23:59:59+00:00 $ date -uIs -d @0000-12-31T23:59:59+00:00 date: invalid date ‘@0000-12-31T23:59:59+00:00’ $ If date thinks it's valid ISO 8601 when it outputs it, I'd expect it to be considered valid input to take back. Cheers, Ralph.