As every alert person is bound to know by now, we are adding a free extra second -- a "leap second" -- to our day, once and once only, today, June 30.

By setting back our clocks one second just before 8 p.m., we hope to keep up with the sun, the only author and source of correct time.

Citizens must be careful, of course. You don't want to be all thumbs and set the clock back two seconds. With a little practice anybody can learn to adjust the clock one second. The International Time Bureau keeps track of all this sort of thing and says we're all right if we just remember the June second.

Every year from 1972 through 1979 we have, of course, been faithfully inserting a leap second at the close of New Year's Eve. And in 1972, you recall, we had to set back our clocks a second in June as well. But then in 1980 we had a year off and did not insert any leap seconds at all. Now, this month, we pay for the year off by having to add a second and, furthermore, we are going to have to add another second in June of next year, though we will not have to remember to add any seconds on New Year's Eve, which is a respite.

There are days you wake up and say, "Surely it's not Wednesday already?"

That is because our slothful ancestors in the dark centuries before us let an endless number of years go by without adding their leap seconds. Things got behind. We have paid for it ever since.