When my friend Harry was a child, his grandfather took him on his knee one spring and explained to him about April Fool's Day. Then, Grandfather recruited Grandson to play a trick on their common nemesis: the man in between them who was son to one and father to the other.

The prank? Substitute salt for sugar in the sugar bowl.It was done. And Harry howled with delight as his father stirred a heaping teaspoon of salt into his morning coffee. His father was good-natured about the joke - laughed himself silly, as a matter of fact.

Harry repeated the gag several years in a row, and neither his father nor he tired of the mini-vaudeville act. But Harry didn't know that his father laughed so hard because he anticipated the prank and always got up a little early to switch the bowl's contents back from salt to sugar.

Years later, Harry learned from his grandmother that this salt-for-sugar joke had begun when Harry's dad had done it to his father. The grandfather had finally turned the tables on his son by co-opting his grandson.

So, now you know why my friend Harry was in such a good mood on April Fool's Day this year. There was salt in the sugar bowl again - at Harry's house and his son's house, as well.

The joke is rather dumb and certainly not original, but I like its essential foolishness. And there is health in seeing the salt-sugar prank as a metaphor for the bittersweet nature of father-son relationships. In observing this April gesture from generation to generation, the men have shaped a sacred habit out of a common gag. No longer just a joke, the salt in the sugar bowl has become a serious statement of connection - an annual gift between generations that comes wrapped in laughter.

My favorite holy day is the first of April - the Day of Fools, of which I am certainly one.

It's not a legal holiday and has never been declared by any president or legislative body. Like Valentine's Day and Halloween, April Fool's Day belongs to distinct dimensions of the human race that don't need legal status to be recognized or celebrated: love, fear and stupidity.

The roots of April Fool's Day lie in France. Until King Charles IX came along, Europe kept the Roman tradition of celebrating New Year's Day in the spring at the end of March. Charles officially adopted Jan. 1.

It took quite awhile for the word to get around, and even then, some people remained confused about just what was going on. This group was labeled "poisson d'Avril" - April fish - that is, naive and easily caught. They became the victims of pranks.

The custom spread, and so it continues unto this day. April Fool's Day commemorates mischief, which, more often than not, we bring upon ourselves because we aren't always in the groove of what's going on.

This explanation of the origins of the Day of Fools is vague and confusing. Nobody even really knows where the word "April" comes from in the first place. How perfect. An explanation of April Fool's Day shouldn't make too much sense.

Over time, the tradition has become a magnet for something essential in human nature and a rallying flag for those who have - or wish to have - a light heart.

Consider this list of words: clown, blockhead, booby, dolt, nincompoop, ninny, nitwit, jackass, dork, goose, goober, geek and buffoon. You likely will find at least one word in there which you have been called more than once - the term being a shoe that fit you at the time. I've called myself all of them, and I wear the labels with pride.

April Fool's Day has taken on private ritual purpose for me, and I celebrate it with both care and abandonment, lest I shrivel up and die from taking myself too seriously.

P.S.: April 1 this year has exceptional meaning for me. Appropriately, it's the publication date of a book I've written about those sacred habits and rites of passage that give life meaningful structure and purpose - like April Fool's Day. The book is called "From Beginning to End, the Rituals of our Lives." (No fooling.)