Because if you start the jokes on April 1st.... let's just say it'll be too obvious. So yeah. Start them.
Before April first comes around, I would like to make a public service announcement. Don't be an ass. Don't ask out anybody because you think it would be funny to dump them. Don't say you're dead. Do. not. psychically. or. emotionally. hurt. somebody. for. your. own. entertainment. Do not take things too far. And basically, just have common sense. Yeah a whoopee cushion would be a nice prank (ha, one of the oldest tricks in the book), but smearing ketchup all over the kitchen floor and laying in it pretending you're dead and having mom/dad clean it up is terrible.