[Simucal]

That seems like an odd thing to do when employees have unlimited vacation time. "Oh, I'm out of sick days? I'll just take a vacation day then."

[ghshephard]

Vacation needs to be negotiated in advance with your manager, and you need to make sure all your projects are taken care of. In theory, your manager can't deny you a sick day, and they don't need to be negotiated.