Santos Inocentes.
 

Today is Spanish April Fool's Day, they don't do it on April 1st.
It is called El Dia de los Santos Inocentes and the TV this morning showed somewhere in Spain where they were having a "battle" with flour and eggs, what a mess but it looked like great fun :D;).
I don't think pranks and jokes finish at noon like in the UK, read this on Wikipedia Día de los Santos Inocentes - Wikipedia, la enciclopedia libre :D