What was going on when I was born?

International Britain rejected an appeal from the United Nations for further negotiations on the Falkland Islands dispute, and the Cabinet was said to authorize the British battle fleet in the South Atlantic to open a new assault. In rejecting the appeal, Prime Minister Margaret Thatcher told the House of Commons that Argentina had in effect turned down Britain's final proposals for a settlement and that ''it is inconceivable that they would now come genuinely to accept'' the ideas proposed Wednesday night by United Nations Secretary General Javier Perez de Cuellar. (Page A1, Columns 3-6.) Argentina braced for a possible attack by Britain on the Falkland Islands, while Foreign Minister Nicanor Costa Mendez insisted that Argentina still considered the United Nations mediation effort to be alive. ''Argentina is engaged in the mission of the Secretary General, and it continues to insist upon his mission,'' the Foreign Minister said at a news conference, apparently before learning that Secretary General Javier Perez de Cuellar said tonight in New York that his peace efforts had failed. (A1:4-5.)

OPEC oil ministers expressed sharply different views today about whether to abandon their two-month-old program to limit output by the 13 member nations, now that falling prices seem to have stabilized. The disagreement marked the start of the semiannual meeting here of the Organization of Petroleum Exporting Countries. The session opened amid considerable pomp, as OPEC celebrated what it considers its success in managing production levels. ''It's very important for OPEC to move toward permanent controls,'' said Belkacem Nabi, Algeria's Minister of Energy and Petrochemical Industries, before the meetings.

A class-action suit was filed against the state yesterday on behalf of the estimated 6,000 homeless men and women who have been released from state psychiatric hospitals and now live on the streets of New York City. The suit seeks a court order directing the state to provide residential facilities for this group of homeless people. It was hailed by Mayor Koch and by City Council President Carol Bellamy.

The Argentine military braced today for a possible British assault on the Falkland Islands, while Foreign Minister Nicanor Costa Mendez insisted that Argentina still considered the United Nations mediation effort to be alive. ''Argentina is engaged in the mission of the Secretary General, and it continues to insist upon his mission,'' the Foreign Minister said at a news conference, apparently before he learned that Secretary General Javier Perez de Cuellar said tonight in New York that his peace efforts had failed. Asked about reports that Peru had presented a new peace plan, Mr. Costa Mendez said it had, but declined to give details. He said the plan ''lay in the realm of diplomatic confidentiality.'' A previous Peruvian plan, presented with the United States, was rejected by Argentina on May 3. On the same day Peru offered military aid to Argentina in its conflict with Britain, an offer that Peru renewed today.

Prime Minister Margaret Thatcher today rejected a United Nations appeal for further negotiations on the Falkland Islands dispute. The Cabinet was said to have authorized the British battle fleet in the South Atlantic to open a new offensive. Mrs. Thatcher told a rapt and expectant House of Commons that the Argentines had in effect turned down Britain's final proposals for a settlement of the seven-week-old crisis. She said that ''it is inconceivable that they would now come genuinely to accept'' new ideas that were proposed Wednesday night by Secretary General Javier Perez de Cuellar. U.N. Chief Concedes Failure At the United Nations, Mr. Perez de Cuellar conceded that his efforts to resolve the crisis had failed and said the conflict could now worsen. (Page A12.)

The House of Representatives, struggling to find a way to help the ailing savings and loan industry, today approved a bill that would set up an $8.5 billion fund to bolster savings and loan associations crippled by high interest rates. The proposal, approved in a 272-to-91 vote, with two abstentions, came despite vigorous opposition from House Republicans. They offered a substitute bill that was defeated in a vote that was generally along party lines. Drafted by the Democratic-controlled House Banking Committee, the proposal is also opposed by the White House, which has expressed concern that the measure would place an unacceptable financial burden on the Treasury, which would back the fund.

Even before it failed to pay $160 million in interest due to about 30 securities firms early this week, Drysdale Government Securities had attracted more attention than appeared warranted by its size and history. The firm, created only in January, with about $28 million of capital, quickly put together a balance sheet totaling an estimated $4 billion or more as it gained a reputation for aggressive trading in Treasury bonds and notes. It was a large leap for a creature spun off from Drysdale Securities, a much older firm with $5.5 million in capital whose trading activity in Treasury issues amounted to only about $700 million just a year ago, according to documents filed with the Securities and Exchange Commission. The confusion inherent in the spin-off company's being larger than its creator is part and parcel of the confusion - of names, of current relationships and of operations - that has surrounded the two firms all week.

The Republican-controlled Senate Friday overwhelmingly rejected Democratic efforts to repeal or defer the third stage of the income tax cut. President Reagan has called the tax cuts, which total 25 percent over three years, the heart of his economic revitalization program. His insistence that the full program be inviolable was a key factor in the breakdown of negotiations for a bipartisan compromise on reducing the budget deficit for the fiscal year 1983, which starts Oct. 1. The Senate budget resolution, as it now stands, would provide $107 billion in new tax revenue over the next three fiscal years. Repealing the third year of the tax cut, which is scheduled to go into effect July 1, 1983, would have added $76.3 billion in revenue.

The Food Notes column of The Living Section on Wednesday misidentified a Manhattan cheese distributor. It is the Marcel Akselrod Company, 530 West 25th Street, New York, N.Y. 10001 (telephone 675-7777).

Over the last five years, the Borough Park section of Brooklyn has become one of the most ambitious centers of residential real estate activity in the city. According to specialists in property sales and mortgage loans, land prices have soared as contractors buy old frame houses on side streets off the main avenues, demolish them and build new two-family and three-family houses. Dilapidated walk-ups have been bought and rebuilt as cooperative apartments selling for $80,000 to $130,000. ''There is tremendous demand, and it has spread to Midwood and sections of Flatbush,'' said Charles Ohlig, executive vice president of the Greater New York Bank for Savings.

FROM the nightmarish vision of violence and death in Tadeusz Kantor's ''Weilopole Weilopole'' to the erotic tableaux vivants of The Talking Band, there is an alluring array of visual and aural imagery on Off Broadway and Off Off Broadway stages this weekend. And, for variety, there is even more than a measure of verbal wit, as in Romulus Linney's ''Goodbye, Howard'' and Jonathan Reynolds's ''Geniuses.'' Although New York's institutional and nonprofit theaters have had their share of artistic disappointments this season, they remain the places where one looks for experimentation and theatrical adventure. Theatergoers can hope to be surprised by an unheralded talent; directors can operate within an ensemble in attempting new modes of artistic communication; playwrights can try to alter their styles, actors can challenge themselves with roles not available to them in the commercial theater. The smaller stages also continue to welcome visiting international companies. This weekend, for example, audiences at Japan House have a singular opportunity to encounter Kayoko Shiraishi, an actress of blazing intensity, in Tadashi Suzuki's eerie Japanese version of ''The Trojan Women.'' And next week Mr. Suzuki and his company will be at Ellen Stewart's La Mama with a bilingual production of ''The Bacchae.''

Because of an error by a Federal spokesman, a United Press International article yesterday incorrectly reported the employment status of Dr. Marc J. Straus, a cancer researcher. He is on the staff of New York Medical College in Valhalla, N.Y. An article appears on page A16.