The day of the Holy Innocents, el dia de los Inocentes, is the Spanish equivalent of April's Fool Day. It is celebrated on December 28th.
Although the day finds its origins in a bloody episode of biblical times (killing of all children less than 2 years old in Belen, ordered by King Herod), it has mostly become a pagan holiday. It is the occasion for people to play pranks at each other and for the media to announce goofy news.