What was going on when I was born?

Four Army paratroopers died and dozens were injured today when a large airdrop designed to test the Pentagon's ability to respond quickly to trouble around the world went awry in the California desert. Later in the day, The Associated Press reported, military officials said that at least 71 soldiers had been injured, three of them critically. Eight other soldiers were also hospitalized.

The offices of the Anti-Defamation League of B'nai B'rith are in a terribly diplomatic part of town, on that long stretch of street across from the United Nations choked with Mercedes Benz automobiles bearing DPL license plates and with quiet square buildings housing organizations like the Turkish Center and the African-American Institute. The Anti-Defamation League building has a tastefully lighted beige lobby and an enormous glass cubicle blocking the elevators. ''No one may go upstairs except by invitation,'' says the security guard in the blue uniform, as though this was Studio 54. By invitation, the New York City transit negotiations are being held inside. There are always undercurrents in this city, and at the end of March, in an even-numbered year, the transit talks are among them. For a time, there are only small signs of activity, like the plumes of smoke that rise sometimes from subway gratings.

The index of leading economic indicators dropped 0.3 percent in February, the 10th consecutive monthly decline, the Commerce Department reported. It said the new figure showed that the economy was still in recession. Officials also revised downward figures reported for December and January. Thus, a December rise of 0.6 percent became a decline of 0.8 percent and a January decline of 0.6 percent became one of 1.2 percent. (Page D1.) The economy will be weaker than predicted in both the second quarter and the second half, according to Treasury Secretary Donald T. Regan. (D1.) President Reagan's economic forecast was rejected as overly optimistic by the G.O.P.-dominated Senate Budget Committee. (D6.) John B. Connally predicted economic chaos if interest rates and projected deficits aren't reduced within 60 days. (A27.)

The JWT Group, parent of the J. Walter Thompson advertising agency, said yesterday that ''irregularities'' previously disclosed in the agency's syndication department exceeded $30 million and that at least two clients had been billed for TV spot commercials they did not get. Previously, Thompson estimated the irregularities at $24.5 million and said that, to the best of its knowledge, none of its clients had been improperly billed. The holding company also said it had concluded that Marie Luisi, senior vice president and head of its JWT Syndication unit and spot media buying, ''was responsible for the improper activities'' and that she was being dismissed as of today. Mrs. Luisi had been suspended without pay since Feb. 3. Mrs. Luisi, reached by telephone and made aware of the company's charges, said she would leave all comment to her lawyer, Ivan S. Fisher. Speaking on her behalf, Mr. Fisher said: ''The days of David and Goliath are over. It doesn't seem likely that this one woman could wreak such havoc unless Thompson is being less than candid.''

The five rightist parties that ran behind the moderate Christian Democrats in Sunday's election said today that they had joined in a caucus aimed at establishing a working majority in the new constituent assembly. Leaders of the collaborating parties said their ''government of national unity'' did not yet constitute a coalition but that they hoped they could produce one by the time the new assembly convenes in mid-April. That development would have the effect of reducing the Christian Democrats, the party that led all the others with some 41 percent of the vote, to a minority opposition role.

The Transport Workers Union and the New York City Transit Authority, in a break with some 45 years of history, have overhauled their collective-bargaining relationship so dramatically that leaders on both sides say there will be no subway and bus strike when the present contract expires at midnight tonight. ''The union has made absolutely no plans for a strike,'' the T.W.U.'s longtime counsel, John O'Donnell, said yesterday. ''The only way there could be any sort of disruption of work would be on a wildcat basis, and there is no indication of that.'' The significance of Mr. O'Donnell's statement, delivered in the same Irish lilt that leaders of the Transport Workers Union have used to announce strikes and threats of strikes since the 1930's, will be lost on few New Yorkers.

FOR the members of the Vazquez family, it is a bittersweet season: In a time when they have been brushed by tragedy, they find themselves on the brink of unequaled circus achievement. The youngest daredevil of the Vazquez clan, 17-year-old Miguel, is the first aerialist to accomplish a recorded completion of a quadruple somersault, a goal that has eluded generations of artists throughout the 123-year history of trapeze flying. His unabashedly partisan family hopes he will be the first to perform the feat before an audience, and he'll be trying tonight when the Ringling Brothers and Barnum & Bailey Circus opens in Madison Square Garden. At the same time, the family is coping with the aftermath of a circus tragedy last month, when the other superstar of the clan, 29-year-old Marguerite, broke her neck when she fell during the most dangerous moment of her routine. ''Every family experiences joy and pain,'' said 25-year-old Patricia Vazquez, who performs with her brother-in-law Miguel, ''and circus families are like any other families. It's just that, with us, it's all out there for everyone to see.''

The broad vote in El Salvador's elections Sunday in spite of a guerrilla sabotage campaign has won the Reagan Administration temporary respite from sharp Congressional criticism and anxiety about American involvement in the Salvadoran civil war. But coupled with the Administration's elation over the size of the turnout is a rising concern that Washington could wind up saddled with a right-wing regime that Congress would balk at supporting or a broader coalition hobbled by internal divisions. ''It's a very delicate time,'' observed Representative Michael D. Barnes, Democrat of Maryland, the chairman of the House Foreign Affairs subcommittee on Inter-American Affairs. ''The big turnout is certainly a very positive sign. The left was set back rather badly in an international public relations sense. But there was no definitive statement by the people about what way they want out of the conflict.''

The third and longest test flight of the space shuttle Columbia ended successfully today with the grace of a soaring eagle dropping out of the sky as the craft came to a smooth landing on a desert of glistening white gypsum sand. After a 50-minute descent from its orbit of the earth, the winged spaceship hove into view in the blue sky over Mockingbird Gap in the San Andres Mountains, glided east over the desert basin, made a wide right turn and, issuing a sonic boom at 20,000 feet, lined up for the landing. Col. Jack R. Lousma of the Marine Corps, the commander, took over manual control at 100 feet and eased the Columbia's rear wheels onto the gypsum surface a few seconds short of 11:05 A.M. The nose reared up and back like a dragon challenged in combat, possibly a result of Colonel Lousma's trying to brake the rollout or from a sudden gust of wind. Flight controllers could not be sure until they talked to the astronauts. Sandstorm Delayed Landing Then Colonel Lousma, with Col. C. Gordon Fullerton of the Air Force, brought the 100-ton craft to a stop, concluding a mission of eight days and five minutes. The flight was extended an extra day because a sandstorm here made a scheduled landing Mondayimpossible.

The judge in the Stouffer's Inn arson and murder trial told a stunned court today, after the last prosecution witness testified, that the case against the defendant was based on ''speculation.'' Speaking in the absence of the jury, the County Court judge, Lawrence N. Martin Jr., declined, however, to dismiss the arson and murder charges against the defendant, Luis Marin. He said such a decision would be ''unappealable and final.'' His rejection of a defense motion to set the defendant free means that the trial will proceed through the defense case and then go to the jury of nine men and three women, who have repeatedly been admonished not to read published accounts of the trial.

An article in Weekend last Friday about Newark's Portuguese neighborhood gave an incorrect telephone number for the Sol-mar Restaurant. The number is (201) 344-3041.

International The five Salvadoran rightist parties that lost to the centrist Christian Democrats in Sunday's elections said they were trying to form a working majority in the Constituent Assembly and that they hoped to establish a coalition by the time the new Assembly convenes in mid-April. A leader of the Christian Democrats, who won 41 percent of the vote, said that the right-wing move would cause ''a tremendous polarization'' of the nation. (Page A1, Column 1.) A Salvadoran rebel leader in exile warned that Sunday's elections had restored the power of the conservative oligarchy and could prolong the civil war. But the leader, Guillermo Manuel Ungo, who is president of the Democratic Revolutionary Front, renewed an offer to negotiate with the new leadership. (A12:5-6.)