What was going on when I was born?

President Reagan said today that the Yurchenko affair, along with two other recent incidents involving Soviet citizens, might constitute a ''deliberate ploy'' to disrupt his coming meeting with Mikhail S. Gorbachev. Mr. Reagan said Vitaly Yurchenko, a K.G.B. officer who had been described by officials as a prized defector, had proven to be of little value. The assessment contradicted assertions by officials and by members of Congress who had been briefed about Mr. Yurchenko by the Central Intelligence Agency. ''The information that he provided was not anything new or sensational,'' Mr. Reagan told a group of news agency reporters. ''It was pretty much information already known to the C.I.A.'' President Voices Suspicion In voicing suspicion that recent incidents might have been staged, Mr. Reagan also mentioned the case of a Soviet soldier who sought refuge in the United States Embassy in Kabul, Afghanistan, and that of a seaman aboard the Soviet cargo ship Marshal Konev in the Mississippi River. Both made apparent moves to defect, then reversed themselves.

''If you had it within your power, complete power, to change one thing in the city over the next four years, what would you do and how would you do it?'' When asked that question yesterday, Mayor Koch proposed that the Legislature repeal the Wicks law - governing bidding on public projects - to ''allow us to build cheaper and better.'' The New York Times posed the same question to 12 other thoughtful New Yorkers. Here are their replies.

Eighteen European governments approved a plan today to increase Europe's technological presence through the development of 10 pilot technology projects. The plan was originally conceived as a civilian counterweight to the United States ''Star Wars'' research program. But there were no concrete proposals to finance the plan, known as Eureka, and most of the projects, ranging from high-powered industrial lasers to a diagnostic kit for gonorrhea, were under discussion well before the initiative was proposed by President Francois Mitterrand of France last April. The two-day gathering of foreign and research ministers came against the backdrop of discussions in several European countries over whether to support the Reagan Administration's $26 billion five-year research program into an antiballistic missile shield, the Strategic Defense Initiative, popularly known as Star Wars.

The General Accounting Office charged today that the awarding of Social Security's largest consulting contract was flawed by serious irregularities and potential conflicts of interest on the part of several officials, including John A. Svahn, who was Commissioner of Social Security at the time. Mr. Svahn, now President Reagan's assistant for policy development, was accused of giving his former employer a special advantage in competition for a multimillion-dollar contract to help modernize Social Security's computers. Mr. Svahn and representatives of the firm, Deloitte Haskins & Sells, denied doing anything wrong. Milton J. Socolar, special assistant to the Comptroller General of the United States, testified that Mr. Svahn had allowed Deloitte employees to use space in and near his office suite at the Social Security Administration headquarters in Baltimore. The employees, originally part of a Reagan Administration transition team, remained after the team broke up December 1980 as unpaid consultants on computer modernization.

Edgar M. Bronfman, the president of the World Jewish Congress, made a dramatic public appeal last night to John Cardinal O'Connor of New York, urging him to press the Vatican for diplomatic recognition of Israel. In remarks at a dinner honoring the Cardinal for his work in interfaith relations, Mr. Bronfman asked the Cardinal to ''please convey to Rome the importance to Jews everywhere of normalizing relations between the Vatican and Israel, which is home for so much of Jewish culture and so many of the world's Jews.'' The appeal has been made quietly by Jewish leaders many times before, but Mr. Bronfman's decision to confront the Cardinal publicly reflected his organization's discontent with the Roman Catholic Church's progress in healing centuries-old wounds in the Jewish community, particularly in its refusal to recognize Israel. No Reply by Cardinal The Cardinal did not reply to Mr. Bronfman's appeal at the dinner, but he later told reporters he had ''no hesitancy at all'' about discussing the issue with the Vatican Secretary of State, Agostino Cardinal Casaroli, or with Pope John Paul II. ''But it would be presumptuous of me to think I could do more than that, to express the feelings of the Jewish community that I meet here in New York. And I have great trust in the understanding of the questions on the part of the Holy See.''

OF all the rooms in the house, the kitchen is perhaps the most expensive to renovate. Such renovations can be the most complicated; they can take the longest. And they are by far the most common. According to a recent projection by the National Association of the Remodeling Industry, $6.9 billion will be spent on the renovation of kitchens in the United States this year, compared with $5.7 billion spent on room additions, $3.9 billion on bathrooms and $2.5 billion on family rooms. ''Ever since the dramatic change in the interest-rate structure in 1980, we have seen more renovation than new construction,'' said Martha Kerr, executive vice president of Neil Kelly Designers and Remodelers in Portland, Ore., and president of the National Kitchen and Bath Association. ''People are choosing to stay in existing homes and modify those homes to accommodate their changing life styles.''

Only hours after his election with a record percentage of the vote, Mayor Koch yesterday proposed that the city use at least part of its budget surplus to reduce business taxes if the city's economic recovery continued. He said he favored a reduction in these taxes until the city's business taxes were at the median level of all 50 states. He added that such a tax reduction ''will enhance the number of jobs in this city.'' At the same time, Mr. Koch risked antagonizing many business interests when he suggested that midtown truck deliveries be barred during the day to ease traffic.

With a concerted push from institutional investors in the waning minutes of trading, the Dow Jones industrial average jumped the historic 1,400 hurdle yesterday with relative ease, ending the day at 1,403.44. Many professional traders believed that the 1,400 plateau would be difficult to surmount without a resting period of at least a few days, and maybe even weeks, after the Dow moved close on Tuesday with a close of 1,396.67. But a surge of enthusiasm for equities carried over from recent sessions as investors were encouraged that interest rates would fall. At times yesterday, it seemed as if the indicator of 30 blue-chip stocks had given up the quest. While the Dow passed the 1,400 level in both midmorning and midafternoon trading, it was down 1.60 points with only 30 minutes left in the session, putting it 5 points below 1,400.

In his first direct criticism of Congressional tax-writers, President Reagan declared today that he was dissatisfied ''with some of the waterings down that are taking place as they discuss it.'' Speaking to about 200 campaign workers on the first anniversary of his re-election, Mr. Reagan said, ''We need the kind of tax reform that we originally proposed.'' In recent weeks the House Ways and Means Committee has modified many of the President's tax proposals as the chairman, Representative Dan Rostenkowski, Democrat of Illinois, has worked to forge a majority of his committee for tax revision. The most striking disagreement with the President has been Mr. Rostenkowski's agreement with colleagues that he would not press for abolition of the deductions for state and local tax payments. Elimination of those deductions is a cornerstone of Mr. Reagan's tax plan, and their retention would almost certainly mean that the top tax rate approved by the committee would be higher than the 35 percent proposed by the President.

With less than two weeks remaining before the Geneva meeting between President Reagan and Mikhail S. Gorbachev, there is only the slimmest possibility that the talks will produce more than a thorough discussion of each side's views, American officials who just returned from Moscow said today. They also said there was a chance there could be some accords on modest issues. Secretary of State George P. Shultz and Robert C. McFarlane, the national security adviser, returned to Washington this afternoon to report to Mr. Reagan about their two days in Moscow. They said the discussions in Moscow ended with the United States and the Soviet Union still far apart on arms-control issues and regional disputes.

''I don't think the negotiation of facts and figures about which weapons and how many and numbers and so forth in weaponry should take place at the summit.

Markets The Dow Jones industrial average closed above 1,400 for the first time, helped by a late surge in trading by institutional investors. The average finished the day at 1,403.44, for a gain of 6.77 points, after being down 1.60 points a half-hour before the close. The Dow has been generally climbing since crossing 1,300 in May, and most traders took the latest gain in stride. There were only feeble gains in the broader indicators, with most of them still several points below their records. Volume widened to 129.5 million shares, from 119.2 million. [Page D1.] Prices of Treasury issues fell modestly, in what dealers said was a normal retrenchment after the six-day rally in the credit markets. [D21.] The largest tax-exempt bond issue ever was announced by the New Jersey Turnpike Authority. The $2 billion sale, more than double the previous largest issue, will be used to widen the turnpike. [D21.] Yields on money market mutual funds inched higher in the latest week. [D24.]