Seconds don't matter for sunset and sunrise to humans. Move a bit and your off no matter what timezone you are in. If you need really really precise sunset and sunrise leap seconds don't help. You are more likely to hit a bug than be helped by them. I'm all for ending leap seconds and ending daylight savings while we at it. In Spain, in summer, some people start work at 08:00 or 07:00, no need to change clocks to change habits.