What was going on when I was born?

Several thousand students of Christian schools came by bus and plane from across North America to march in New York City yesterday. For two hours, to the thump and brass of such selections as ''Onward, Christian Soldiers'' and ''The Marine Corps Hymn,'' the youngsters and their teachers paraded down Central Park West, some in coats and ties. 'We thought it was going to be terrible,'' said Druman Heron, 17 years old, who came with eight schoolmates on a yellow bus from the Tecumseh Christian Academy School in Tecumseh, Okla. ''We thought people would be throwing eggs and water balloons.''

The Polish Communist Party has now defied Moscow and runs the risk of being branded a renegade in the Soviet bloc. By keeping Stanislaw Kania as party leader, the Central Committee$ in effect, turned its back on a warning from the Soviet Union that a new leadership must be installed to halt the course that Poland was following. ''Yesterday, it looked like the Politburo was not afraid of Russia, and today it looks like the Central Commuttee isn't either,'' a Polish diplomat said. He was summing up a two-day Central Committee meeting that ended early today with Mr. Kania still in power despite a campaign to oust him by hard-liners led by Tadeusz Grabski, a Politburo member.

IMPROVISATIONAL comedy is essentially impudent madness. Because virtually all of it is created at the moment, often out of current experience and usually at the suggestion of audiences, it has little time for such niceties as taste and taboos. Improvisational comics must be fast on their feet and quick with their tongues. Inventiveness and situations count, not gags. As a genre, modern improvisational comedy grew out of the intellectual ferment of the University of Chicago in 1955, and its golden age of comedic glory began in 1959 when the Second City improvisational group opened its own theater in a converted laundry. Some of its members came from such predecessors as the Compass Players and the Playwrights Theater Club. The movement was to spread in the 1960's from coast to coast, from the Committee in San Francisco to the Premise in New York, and it was to reshape American comedy.

Sales by the nation's retailers rose by two-tenths of 1 percent last month following a 2.1 percent decline in April that was the biggest dip in more than seven years, the Commerce Department reported today. The newly revised April decline, originally reported at 1 percent, resulted mostly from an 11.2 percent drop in automobile sales as spring rebate programs ended. In fact, the auto rebates have accounted for most of the recent changes in retail sales, the Commerce Department figures indicated. Excluding automotive products, the value of retail sales has remained virtually flat for the past two months.

All kinds of ''historical confetti'' have been tucked away in the New York Public Library on Fifth Avenue at 42d Street over the years, and a fair sample will be tossed out for viewing in Astor Hall at the main entrance starting today. Speakeasy cards, a leaflet declaring ''Save the 15-cent fare!'' Tom Thumb's greeting card and anti-Nazi literature from the German underground concealed in packets of tea are just a few of the items displayed in ''Typographical Small Wares: Ephemera From the Collections.'' Impossible to catalogue, the items are filed in scrapbooks and envelopes that are seldom exhibited. The earliest item in the display is a Roman Cathoic indulgence, sold by the Church in 1480 to laymen who wanted absolution for their sins. ISLE OF GREECE IN HEMPSTEAD A Grecian festival will transform the three-acre grounds of St. Paul's Greek Orthodox Church at 110 Cathedral Avenue in Hempstead, L.I., today through Sunday. Bouzouki music, folk dancing and all kinds of Greek food and wine will be offered. A taverna will serve full dinners with entertainment. Outdoor food sites will include a gyro and sausage pit. In a garden arbor, wines from various districts and islands will be offered, along with snacks such as spinach and cheese pies. Games, boutiques, a flea market and an art gallery are also planned. For travel and other information: (516) 483-5700.

Marvin Miller, executive director of the Major League Baseball Players Association, announced early today that the players were on strike. Emerging from the third session of a long day between negotiators for club owners and players in New York, Mr. Miller said, ''We have been meeting most of the day, we have accomplished nothing. The strike is on.'' The strike is the players' third in the last 10 years, but it is the first to start dur- Issues in the strike, page A22. ing the regular season. There was no immediate indication how long the strike might last, but there was a considerable distance between the sides in their bargaining postures.

The time of the Beethoven Society concert scheduled for tomorrow was listed incorrectly in last Sundays's Arts and Leisure Section. The concert, to be performed by the New York Vocal Arts Ensemble, Robert White, tenor, and the Aspen Soloists, will be given at Alice Tully Hall at 3 P.M.

As the price of silver declines on commodity exchanges, the price tags on those proverbial silver spoons - not to mention knives and forks - are also slipping. But with silver's reputation tarnished by its dramatic price upheavals in recent years, consumers and the stores that sell to them are proving wary of buying the sterling silver place settings and tea services that may once have been the hallmark of a civilized life. Since it reached a spot-price peak of $48 an ounce on Jan. 22, 1980, the price of silver has dropped steadily. Last week it dipped below $10 an ounce for the first time in two years, and closed yesterday in New York at $10.24.

Voting is heavy in Irish parlia- mentary election A2 Senate confirms Rashish in State Department post A3 East German paper uses dispar- aging style for Polish leader A4 Around the World A5 U.S. envoy ends talks with Botha on Namibia A6 U.S. Jewish groups rally to Is- rael's side A8 Visit to Egypt by Peres, Israeli op- position leader, is put off A10 French Communists hope to pick fruits of Mitterrand victory A10 Teheran demonstrators call for trial of Bani-Sadr A11 Government/Politics Regents upheld in denying ac- creditation to Moon sect school B2 New York City Republicans meet to endorse Koch B3 Republican leaders are promised a wider role in filling U.S. jobs B5 Rights panel suggests "state- hood" for Indians D14 Energy Two studies support Con Ed's plan to convert three plants to coal B3 General Around the Nation A12 Coast Guard cautions boaters in metropolitan area B4 The trial of several people on drug charges started Manhattan D14 Education/Welfare Sarah Lawrence College picks ex- Carter aide as eighth president B2 Religion Baptists calm their differences and affirm pluralism D14 Features/Notes Notes on People B4 About Washington: The other gov- ernment B6 Weekend Weekender Guide C1 Flea markets in season all over the region C1 Improvisational comedy thriving in New York C1 Theater: Broadway C2 "A Tale Told" at the Circle Rep C3 Screen: "Richard's Things" with Liv Ullmann C13 At the Movies C6 "History of the World - Part I" by Mel Brooks C14 "Clash of the Titans," with Oli- vier as Zeus C6 Spielberg and Lucas's "Raiders of the Lost Ark" C10 Dance: A May O'Donnell festival at the Public C15 Music: Eve Queler ferrets out an- other composer C3 Cuban jazz emigres find haven in 52d St. loft C12 A Red Norvo Trio reunion C12 Art: Art People C21 Houdon busts at the Frick C19 Auctions C22 Books: Publishing C24 Reissue of A.J. Liebling collecC25 The truly needy, continued Protracted war on cancer Don't write off Bangladesh What the camera didn't show Letters A26 Tom Wicker: the high cost of poli- tics A27 Flora Lewis: Baghdad, the sequel to Hiroshima A27 Robert Rudney: now, Mitter- rand's second hurdle A27 Ben Albert: the age of spite in America A27

''The threatening tone of the recent letter from the Central Committee of the Communist Party of the Soviet Union, a text of which has just become available, amounts in our view to interference in the internal affairs of Poland.'' - David Passage, the State Department spokesman. (A3:4.)

Japanese auto makers, facing restrictions on exports to the United States, are locked in tough negotiations with their Government over just how many cars are to be shipped during the next few years. Beyond the American market, however, the results of these talks could have an even broader impact on Japan's most profitable export industry. The arrangements that are worked out, analysts say, not only will tend to freeze each company's market share in the United States but also are likely to be the basis for similar export agreements with other countries. Because of the complex haggling with the auto industry, Tokyo officials have done little to enforce the recent export agreement with the United States. ''So far the trade ministry just watches the quarterly export figures,'' a leading auto executive said.

President Reagan appealed to 350 supporters to help win Congressional passage of the Administration's tax bill. He told the group, which had helped muster support for his budget, that he needed another ''vital bipartisan piece of legislation'' - his 25 percent, phased-in reduction in tax rates. Earlier, Mr. Reagan told labor leaders he would not compromise on the cut. (Page A1.) A lack of real economic growth in the next two quarters is predicted by two top Adminstration economists, after the 8.5 percent inflation-adjusted growth rate in the first quarter. Beryl W. Sprinkel, Treasury Under Secretary for Monetary Affairs, said he did not expect the slowdown to be long-lasting or deep. The same outline was also presented by Murray L. Weidenbaum, chairman of the Council of Economic Advisers. It was the first time the Administration had made such specific predictions, and they were viewed by private economists as realistic. (D1.)