Sort of a cross-cultural version of the 57 state gaffe:
El Presidente Obama celebrates 'Cinco de Cuatro' | Top of the Ticket | Los Angeles Times: "President Obama greeted a White House crowd this afternoon gathered for a May 4 premature celebration of Cinco de Mayo, the Mexican holiday honoring an upset military victory over the French, whose troops didn't do so well in North America and don't celebrate the same day much.
Anyway, in a well-intentioned attempt at Spanish and a joke about being a day early, Obama said:
'Bienvenidos. Welcome to Cinco de Cuatro -- (laughter) -- Cinco de Mayo at the White House. We are a day early, but we always like to get a head start here at the Obama White House.'
Apparently unbeknownst to the president he wasn't saying 'Happy May 4th.' He was saying, 'Happy fifth of fourth.'"