Source : Free On-Line Dictionary of Computing

April Fool's Joke
     
         (AFJ) Elaborate April Fool's hoaxes are a
        long-established tradition on {Usenet} and {Internet}; see
        {kremvax} for an example.  In fact, April Fool's Day is the
        *only* seasonal holiday marked by customary observances on the
        hacker networks.
     
        (1995-01-25)