Lordy, here it is Leap Year again, time to call at Mike Palm's Restaurant & Rathskeller on Pennsylvania Avenue.

It happens every four years, our visit to the Palm family, for on Feb. 29, 1948, they had a son, Myron Jr., and four years later on the same date they had another son, Herbert.

Mike Sr. died six years ago, but his wife carries on the place just east of the Capitol, along with their daughter Patricia (Sept. 8), the sons having gone into business.

"I can top that," said Lillian Palm. "My daytime bartender was born on my seconds son's birthday. I got a 7-year-old bartender here."

They are observing Sadie Hawkins Dat at the restaurant, with drinks half-price for any man brought in by a woman.

Now, Sadie Hawkins Day is not strictly correct here, being an annual girl-meets-boy affair borrowed from Li'l Abner. The idea of Leap Year is even older than Al Capp, going back to 1288, when the Scots passed a law providing:

"For ilk yeare knowne as lepe yeare, ilk mayden ladye of bothe highe and lowe estait shall hae liberte to bespeke ye man she likes."

Not that it has ever made much difference. The literal-minded may check marriage license statistics, but in point of fact, romantic pursuit can't be measured like a horse race. You don't win a waltz.

Peculiar things happen on Leap Year Day. In Aurora, Ill., it is illegal, by city ordinance, to be a bachelor on this day, and on one recent Feb. 29 some 200 bachelors were arrested there by women wearing police uniforms, handcuffed and jailed.

St. Patrick, distressed at the low marriage rate in Ireland, suggested that females be allowed to propose during Leap Year and also fined bachelors one silk gown. It doesn't say who got the silk gown.

According to The Book of Days, St. Oswald died on Feb. 29, 992. There now, you didn't even know there was a St. Oswald.

Leap Year Day, being not a real day (if you get paid by the month, you donate that day to your boss), was celebrated in saloons past with a drink on the house, since the day was rent-free.

Anyway, as days go, it is the most necessary day we have, even more necessary than the Fourth of July. Because without it, the calendar would by now be irritatingly jumbled.

The problem was that the earth takes slightly more than 365 days to orbit the sun. In 46 B.C. Julius Ceasar set up an extra day every four years, which seemed just right, for at the time everyone thought the year was exactly 365.25 days long.

However, it turned out that the year actually is 365.2422 days long. That little difference, .0078 of a day per year, comes to three days every four centuries, and by the 16th century Easter was beginning to slide into midsummer.

So Pope Gregory XIII refined Leap Year. The extra day now was added only to those century years evenly divisible by 400, for example, 1600 and the one just ahead of us, 2000. But on the other century years, 1700, 1800, and 1900, there was no Feb. 29 even though those were supposed to be Leap Years.

Well, there you are. We don't have to think about it for another four years. Good luck to the Palm family, and we'll see you in '84, and maybe the daytime bartender too. He'll be 8 by then. CAPTION: Illustration, "Li'l Abner," Al Capp; Copyright (c) United Feature Syndicate