What was going on when I was born?

On the eve of John W. Hinckley Jr.'s trial in the shooting of President Reagan and three other men, a prosecutor told the judge today that Government psychiatrists do not believe Mr. Hinckley was so mentally ill at the time that he was not responsible for his actions. The statement by Assistant United States Attorney Roger M. Adelman was made to Federal District Judge Barrington D. Parker at one of several hearings today on disputed issues. With some of these issues still unresolved, the trial was set to begin Tuesday amid the most extensive security measures that guards at the Federal Courthouse here could remember. The central issue at the trial will not be whether Mr. Hinckley committed the criminal acts with which he is charged, but whether he should be excused from responsibility for his actions because of mental illness at the time. Under the legal test used by Federal courts here and elsewhere, the jury must find Mr. Hinckley not guilty by reason of insanity if it decides that at that time, as a result of mental disease or defect, he ''either lacked substantial capacity to conform his conduct to the requirements of the law, or lacked substantial capacity to appreciate the wrongfulness of his conduct.''

Prime Minister Margaret Thatcher suggested strongly today that further British military action in the Falkland Islands crisis might be imminent and warned that ''time is getting extremely short'' for further diplomatic initiatives. Mrs. Thatcher told the House of Commons this afternoon that the British recapture of South Georgia, 800 miles east of the Falklands, had been com- Transcript of statement, page A12. pleted at 10 A.M. today without British casualties and with serious injury to only one Argentine defender. She said Britain had not fired the first shots, and she promised that almost 200 Argentine prisoners taken in the operation would be quickly sent home.

The following article is based on reporting by Leslie Maitland and Michael Oreskes and was written by Mr. Oreskes. At least 18 law enforcement agencies are involved in investigating corruption in New York City's multibillion-dollar construction industry, but key prosecutors agree that they are doing less than they would like to do about the problem. Officials of these agencies insist that it is not a lack of interest that has stymied strong action, although they say the issue has provoked little outcry and seems to be low on the list of the public's priorities. Many prosecutors complained that a major reason they could not do as much as they would like to root out corruption in the construction trades was a lack of cooperation from the industry. They suggested that this was in large part because witnesses were afraid of economic or physical retaliation.

THESE were no ordinary storm clouds. Moving in from the west across the Belize-Mexican border, they rapidly covered the entire evening sky. They were a strange yellow-gray, billowing and soaring awesomely like thunderheads, though not organized into a clearly defined storm. Then, at the archeological camp of the Peabody Foundation near Orange Walk, Belize, we learned that, after days of eruption, El Chichon volcano, 300 miles to the west in Mexico, had exploded a few hours earlier. Powdery ash, like very fine snow, began sifting down and soon the entire landscape was covered.

WOOLLEY, Wash. -Small lumber mills that harvest much of Washington's Douglas fir, hemlock and red cedar are now embroiled in a contract dispute that has put the industry and state goverment at odds with local communities. The quarrel took shape earlier this month, when the State Legislature passed a law waiving penalties for 15 mills that defaulted on contracts to clear timber from state-managed forests. The mills, hurt by recession, high interest rates and a depressed housing industry, contended that the contract price for the timber was much too high.

Eastern Airlines won tentative C.A.B. approval to take over Braniff's Latin American routes for at least a year, beginning June 1. Eastern originally offered to pay Braniff $30 million to lease the routes for six years. Braniff had asked the board to allow either the Eastern plan or an earlier one from Pan Am. (Page A1.) G.M. reported a first-quarter profit of $128.3 million. It said, however, that the profit resulted from finance subsidiaries and foreign currency dealings rather than auto production. The company earned $190 million in the 1981 period. (D1.)

KILLING the Department of Education is turning out to be harder than its would-be pallbearers imagined. Neither outright abolition, originally pledged by President Reagan, nor transformation into a foundation for educational assistance, favored by T.H. Bell, the Secretary of Education, now seems imminent. Congress appears in no mood to rescind what it so recently created. Neither is Mr. Bell in a mood to give up his plan to create a foundation. He denies any intention to resign, as had been rumored in recent weeks. ''I'm not planning to leave,'' he said in a telephone interview. ''I'm planning to be right here and carry out my responsibilities.''

A $3 million gift to help replace Columbia Univerity's deteriorating 54-year-old Baker Field football stadium with a new concrete structure was announced by the university yesterday. The new stadium will be on the same site at the northwestern tip of Manhattan, 218th Street and Broadway. The donor is Lawrence A. Wien, a lawyer and philanthropist with an estimated $2 billion worth of real-estate holdings around the country, including the lease on the Empire State Building. A fund-raising campaign for the new stadium is about to start, No formal cost estimate has yet been made, but Mr. Wien said Columbia's president, Michael I. Sovern, had told him the minimum cost could be $7 million. Other estimates have run as high as $15 million for an entire complex.

The American Telephone and Telegraph Company said yesterday that it plans to sell up to 10 million shares of newly issued common stock under the Securities and Exchange Commission's experimental shelf rule. Instead of selling all the new stock at once through a syndicate of underwriters, as has been traditionally done, A.T.&T. will be able to sell the shares in parcels from time of time through underwriters, broker-dealers or directly to institutional investors. If all the new shares are sold, the $500 million to $600 million raised would help finance capital spending by A.T.&T., whose ability to borrow money is being restricted by the pending divestiture of its operating companies. An S.E.C. spokesman, Chiles Larson, said that A.T.&T. was perhaps the first company to register for the sale of stock under the S.E.C.'s Rule 415, which took effect in March on a nine-month experimental basis. Other companies have registered to sell bonds and other debt offerings under the ruling, which is expected to dramatically transform the investment banking business by giving large corporate clients the flexibility to market securities without investment bankers as intermediaries.

The Critics' Choices column in The Guide on Sunday gave an incorrect date for a block party in Shubert Alley in tribute to Duke Ellington. It will take place tomorrow at noon.

Victor Posner, a 63-year-old financier with controlling interests in several enterprises, including the Sharon Steel Corporation, was indicted in New York yesterday on charges that he had evaded $1.25 million in Federal income taxes by inflating the value of land that he had donated to a college. The 12-count Federal indictment charges Mr. Posner with conspiracy, tax evasion and the filing of false tax returns for the years 1975 through 1979. He could face up to five years in prison on each of several counts if convicted. Mr. Posner, a Miami Beach resident who is often in the news for his efforts to acquire other companies, owns assets with a reported worth of $1 billion. He is chairman and chief executive officer of Sharon Steel, a major domestic producer of specialty steels with annual sales of about $800 million.

AWILDLIFE biologist who has been monitoring the plight of the black-footed ferret for the last 10 years has found at least 22 of them alive, well and breeding on the plains of Wyoming near Cody. The discovery by Timothy Clark of Idaho State University has raised hope that the species, unique to North America and believed to have been reduced to only one or two living specimens, may be making a comeback. Dr. Clark's findings were announced by the Wildlife Preservation Trust, a Philadelphia-based conservation organization. In the early 1970's several ferrets were captured and attempts were made to breed them at the Patuxent Wildlife Research Center in Maryland. But their offspring did not survive and by 1978 the last captive ferret had died. At that time there had been no verified reports of black-footed ferrets in the wild for several years.