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1.
March 18th, the day after St. Patty's day and the only day on which more people are hung over than the day following the New Year.
Well ill be its International Hangover Day, looks like we should clean the toilets, they're probably full of good Irishmen's vomit! Hooray
by SeanThornton March 17, 2013
 
2.
Because everybody in the world celebrates new years eve. Not just America... And they party way harder too. Aussie aussie aussie oi oi oi
During the night before InterNational Hangover day... Getting on public transport and befriending anyone who'll tell them wat state they ended up in, and to help them get home again. Even if they're 600ks away from home with nothing. And being 16 year old to boot.
by Vladimiskarnavich January 06, 2007