It's like a snowday for students, but instead of snow causing the canceling of educational facilities, its swine flu. Can refer to any closing due to the H1N1 virus.
We had a Swineday today because 20% of the kids had swine flu.
A day off when at least one person has a suspected, I mean suspected, case of the H1N1 virus. It could be just a pollen allergy or a little food poisoning the mimics the swine flu.
My school had to have a swine day because the nurse thought Timmy had a case of the H1N1 virus, even though it was a little case of the sniffles.