What was going on when I was born?

John W. Hinckley Jr., who shot and wounded President Reagan in March 1981, made an unannounced court appearance today and said ''I am ready now'' to seek a ''release hearing.'' Speaking in a strong, clear voice, Mr. Hinckley stood before Federal District Judge Barrington D. Parker and said, ''I have talked to some doctors and they want to back me up.'' He did not identify the doctors. Courtroom observers understood Mr. Hinckley to be seeking complete freedom from St. Elizabeths Hospital, where he has been held since June 1982, when a jury found him not guilty by reason of insanity in the shootings of Mr. Reagan and three other men. Under a special act of Congress applicable only in the District of Columbia, Mr. Hinckley is entitled to be released from the mental hospital if he can prove that he is no longer dangerous to himself or others by reason of mental illness.

The Common Market was pushed into a new financial crisis today, barely a month after its leaders said they had resolved its protracted internal quarrels over money. In an unusual display of one of its few powers, the European Parliament, meeting in Strasbourg, voted 212 to 70 to block payment of a $600 million budget rebate that leaders of the market had promised Britain this year. The pledge was part of the Fontainebleau summit accord last month on reforming the finances of the trading bloc, whose formal name is the European Economic Community. That agreement was supposed to end the bitter disputes over the community's runaway farm spending and Britain's complaint that it pays an unfair share of it. The quarrel had virtually paralyzed the Common Market for the preceding four years.

The hour has come. The Games of the XXIII Olympiad will begin Saturday with extravagant opening ceremonies worthy of their Hollywood setting. The Los Angeles Memorial Coliseum will be packed to its 93,000 capacity with tickets costing $200, $100 or $50 each. The organizers will spend $7 million for the opening and closing ceremonies alone.

The chief engineer for the manufacturer of the Navy's F-18 aircraft said today that the company's tests a decade ago underestimated the stress that has caused cracks in the jet's tail. ''Had we properly assessed it, we would have designed for it and not had the problems we have,'' Don Snyder, director of F-18 engineering at the McDonnell Douglas Corporation, said in a telephone interview. His statement came amid preliminary jockeying between the Navy and McDonnell over which should pay to repair the F-18's, billed as the service's most versatile warplane. The Navy announced this week that it had restricted the way F-18's could be flown until a design problem that sometimes causes violent air currents to buffet the plane's tail was corrected. In January, according to a Navy spokesman, cracks were discovered in F-18's at the Naval Air Test Center in Patuxent River, Md. An order to restrict flying to unstressful conditions was issued July 14.

George Gallup developed polling into an important force in the world. An appreciation, page 9. George H. Gallup, an inquisitive Iowan who pioneered in the techniques of public opinion polling and did much to make it a key tool of politics, government, business and scholarship, has died at his summer home in Switzerland. He was 82 years old. Speaking from Princeton, N.J., where Dr. Gallup had his headquarters, his assistant, Sarah H. Van Allen, said he died Thursday at Tschingel, a village near the Lake of Thun in central Switzerland.

New York City led the region to strong gains in employment in the first five months of 1984. Page 27. New York City's economy has continued to rebound from the doldrums of last year, but the growth has bypassed thousands of residents, according to city, state and Federal officials and reports from various industries. The signs of recovery are abundant, with restaurants, movie houses, hotels, financial institutions, the real-estate industry and small businesses showing income running ahead of last year's. The number of jobs in the city is the highest in 10 years and the number of tourists is expected to be the second highest ever.

The Soviet Union said today that the latest United States response to its proposal for talks on space weapons had made such negotiations impossible. Deputy Foreign Minister Viktor G. Komplektov said that the Soviet offer for talks in September remained open, but that ''the current American position makes impossible the conducting of the kind of negotiations we are talking about.'' But Mr. Komplektov, speaking at a news conference, appeared to leave the door open to a change of position based on what he called ''the development of diplomatic contacts.'' Gromyko Accused U.S. His statement was the highest-level Soviet comment on the space negotiations proposal since a speech by Foreign Minister Andrei A. Gromyko on July 2 in which Mr. Gromyko accused Washington of deception and an attempt to avoid talks.

Brazil's military Government, which has long regarded a fast-growing population to be essential to the country's development, has for the first time started promoting an official family- planning program. The change in policy has been under discussion in senior military circles for several years, but it was only formalized last month when the Health Ministry inaugurated a health program primarily intended to make birth-control methods available to poor women. With its population growing by 2.4 percent a year and expected to rise from 130 million today to 180 million in the year 2000, Brazil was until now the most populous developing country in the world without a government family-planning program. 'Acts Like a Steamroller' ''This country will never improve itself by growing in this way,'' Air Brig. Waldyr Vasconcelos, Chief of Staff of the armed forces, said recently. ''This mass acts like a steamroller that crushes all development. Only by controlling births can we benefit from the development achieved over the past 20 years.''

A key House committee has turned down President Reagan's request for additional Salvadoran military aid, and today the Reagan Administration said it would seek a reversal of the rejection. On Thursday the House Appropriations Committee rejected $117 million in more military aid requested by the President, contending that $126 million already provided in 1984 should be enough.

Parliament today approved in principle a new internal security bill that critics have attacked as a return to an era of suppression.

The people of a black South African village have called on Prime Minister P. W. Botha to intervene and prevent their forced removal to so- called tribal homelands under South Africa's system of racial segregation.

President Ferdinand E. Marcos today accused some churches of meddling in Government affairs, an apparent reference to Roman Catholics who have been vocal critics of the Government's human rights policy in the Philippines.