What was going on when I was born?

A major step to govern sea lanes and ocean resources was taken here today when 117 nations signed a treaty codifying law for the seas. The United States and other major industrial nations, such as West Germany and Britain, did not sign. President Reagan has firmly rejected the document, chiefly because of its seabed mining provisions, but the others have not ruled out signing later. Nevertheless, third world delegates at this Caribbean resort loudly applauded the outcome, embraced each other jubilantly and asserted that they had started an effective code.

Producer prices, which signal eventual changes in consumer prices, rose six-tenths of 1 percent in November, more than they have increased most months this year, the Labor Department reported today. Surges in prices for natural gas and home heating oil and smaller rises in gasoline prices caused much of the increase. But the Producer Price Index is still up at an annual rate of only 3.7 percent for the year and is likely to finish in 1982 at the lowest level of increase since a 3.7 percent rise in 1976. The index rose 7 percent in 1981.

The United States and the European Common Market agreed today on steps to defuse a crisis over agricultural exports that has threatened to undermine the Atlantic alliance. After the unusual high-level meeting, both sides sought to give the impression that although differences remained, they could be settled in follow-up meetings set for early next year. A five-man United States Cabinet delegation led by Secretary of State George P. Shultz conferred with five senior officials of the Common Market led by Gaston Thorn, president of the European Commission, which is the executive section of the European Economic Community. Progress at Monetary Meetings Progress was also reported at separate monetary meetings held Thursday and today in Paris and in Kronberg, West Germany. The major industrial nations agreed to make available to poorer nations more than $36 billion to help the recipients repay the tens of billions of dollars in debt that they have accumulated. (Page 42.)

In a building on the edge of the University of California campus here, more than 200 people are preparing for an event that might have bewildered the Olympians of ancient Greece: an Olympiad produced by private enterprise. With 19 months to go before the opening ceremonies, the organizers of the 1984 Summer Olympics say that their goal of staging the games without public funds is on its way and that they expect to end the two-week event with a surplus. The Los Angeles Olympic Organizing Committee, a group of private business and professional people, won the City Council's approval to bid for the Olympics only after committing itself not to use tax revenue. Now, in an effort to fulfill the commitment and avoid the kind of big deficits experienced by most previous host cities, the committee is employing a two-part strategy: using existing facilities for most Olympic competition and using money from private business to finance the Games.

A former diamond dealer was sentenced to 28 years in prison yesterday on fraud and tax charges in a case that the authorities have linked to the killings of at least one witness and three CBS technicians. Irwin M. Margolies, the 47-year-old defendant in the $5 million fraud case, was sentenced by Judge John M. Cannella of Federal District Court in Manhattan. The judge also fined him $72,000 and remanded him to prison immediately. Lawyers familiar with sentencing said the 28-year sentence was one of the longest they could recall in any fraud case.

The United States and its European allies, stressing their willingness to develop trade and human relations, told the new Soviet leadership today that a chance was at hand to rebuild a climate of international trust. In a communique that stressed openness toward the Government of Yuri V. Andropov, the new Soviet party leader, and avoided confrontational language, the foreign ministers of the 16 members of the North Atlantic Treaty Organization called on the Soviet Union for tangible signs that it is seeking a better climate after two years of deteriorated East-West relations. ''The allies are open for all opportunities for dialogue,'' the statement said. ''They will welcome any positive move to reduce tension, and desire, if Soviet attitudes allow, to cooperate in rebuilding international trust.''

President Reagan, pressing for Senate approval of production of the MX missile, said today that he was ''perfectly willing to sit down'' with Congress and see whether there were alternatives to his proposal for basing the missiles. In an unusual Oval Office news conference, the President complained that House opponents of the MX had been News conference transcript, page 10. ''lacking a little in honesty'' and that their rejection Tuesday of funds for production of the first missiles had comforted the Soviet Union. ''If the Soviets are so pleased, perhaps we should be a little more concerned,'' the President said, seated at his work desk.

In a swift and confusing sequence, South Africa appeared this week to wave an olive branch at one of its black neighbor states, then brandished its sword at another. On Wednesday, Foreign Minister Roelof F. Botha and Defense Minister Magnus Malan flew home from what would have apparently remained, had it not been for a press disclosure, secret talks in the Cape Verde Islands with representatives of an Angolan Government that has had South African forces operating almost continuously on its territory. Scarcely 12 hours later, helicopter-borne South African assault teams crossed the border into tiny, landlocked Lesotho - an independent but impoverished state painfully dependent on South Africa - to attack private homes used by members of the African National Congress. By South Africa's own count, 37 people, including 7 innocent bystanders, were killed.

South Africa used ''a lie'' to justify a raid against black exiles that took 37 lives in Lesotho, the Government said today. The Lesotho radio service rejected South Africa's charge that those slain had been staging guerrilla raids into South Africa. It said all the victims were refugees and quoted an unnamed Government spokesman as saying, ''The only real reason why South Africa invaded Lesotho was Lesotho's rejection of apartheid,'' South Africa's policy of racial segregation.

President Kenan Evren is to fly to China on Sunday to begin a five-nation tour of Asia. In his first foreign trip since being elected President in a national referendum on a new Constitution last month, General Evren will spend four days in China, three in Indonesia, three in South Korea, two in Bangladesh and one in Pakistan before returning home Dec. 26.

The Reagan Administration plans to build a $13 million support headquarters in Britain, into which 1,000 staff officers of the United States European Command would move if war began in Europe, senior Administration officials said today. The officials said the support center in High Wycombe, west of London, scheduled to be completed by 1986, would accommodate intelligence, operations, personnel, and logistics officers from the peacetime headquarters in Stuttgart, West Germany, and from the United States. The main mission of the wartime support headquarters would be to assist American commanders on the Continent but not to run the war. The support center would be particularly charged with moving troop reinforcements and supplies from the United States to the battle front.

Administrative and Budgetary Committee - 10:30 A.M. and 3 P.M.