An atheist complained to a Christian co-worker, "Christians have their special holidays, such as Christmas and Easter; and Jews celebrate their holidays, such as Passover and Yom Kippur; . EVERY religion has its holidays. But we atheists," he said, "have no recognized holidays. It's an unfair discrimination." 

"What do you mean, atheists have no holidays," his friend replied, "People have been observing a special day in your honor for years." 

"I don't know what you're talking about," the atheist said, "When is this special day honoring atheists?" 

"April 1st."