BA is the gay mecca in Latin America. The main Pride Parade is held in the streets of downtown Buenos Aires on the first Saturday of November, to celebrate the formation of the first-ever gay group in Buenos Aires in 1969.
Unlike many gay pride events around the world that have a week long celebration with opening events and a closing main event, BA's Pride is merely a very large march in downtown near the Palacio Rosada (their version of the White House, but it's salmon pink). In 2008, the march/parade was on Saturday, 1 November, as it is usually the first Saturday in November. Unfortunately, many gay guides could not pin down the exact dates of events, so many participants did not know exactly when other related events were occuring.
BA does not have a weeklong series of events, so if you do not participate in the march/parade, you may not have known BA Pride happened at all.