The timezone database supports offsets into the seconds, although I've heard some applications will not support files with such offsets iCalendar feeds that they'd otherwise support, so it'd be a bit of a mess still. I can't imagine why a country would feel the need to have an offset measured in seconds, but there are a lot of countries, some of which really don't seem to value global consistency, so it wouldn't be terribly surprising. Combined with countries that insist on applying DST without advanced scheduling, that would be a lot of fun.