Neither did I.
Inauspiciously, the website is currently down (9:09 am), but Wikipedia tells us this much:
International Beer Day (IBD) is an August 5 holiday invented in 2007 in Santa Cruz, CA. As opposed to Oktoberfest, which is in the cold months and largely European, International Beer Day is meant to be celebrated across the world while it's still warm enough for cold beer.I think "International Beer Day" was invented by students at UC Santa Cruz with rare and coveted access to the intertubes. Or maybe it's a put-on. This business about drinking beer "while it's still warm enough for cold beer" strikes me as ... suspicious. (The average high temperature in Santa Cruz in January is sixty degrees.) But if they are having us on, they've managed to get mass media coverage, so good for them. Hoodwinking a journo is its own reward.
International Beer Day is celebrated by drinking beer, drinking beer with friends, and buying beer for others. While there are various other traditions, these seem to be the key attributes. The suggested way to greet someone on International Beer Day is to hand them a beer and say "I bring you the gift of beer". As a general rule, you can't refuse the beer.
In any case, I am prepared to be won over. I will accept gifts of beer all day long. Happy IBD!