What was going on when I was born?

Prime Minister Margaret Thatcher signed a treaty here today giving the Irish Republic a formal consultative role and official presence in this province, long a sectarian battleground. It was the first such arrangement since Ireland's partition 65 years ago. Under the potentially far-reaching accord, the Dublin Government is given a mechanism for pressing its views on virtually all matters touching the Roman Catholicminority here, including the security policies of the army and the police, the administration of justice and prisons. This is to be done through a joint secretariat of Irish and British officials to be set up here, officials said, within a matter of weeks to serve a ''conference'' of Cabinet ministers from the two countries that will be more or less permanently in session to discuss sensitive issues and matters of policy.

Benjamin Rojas stood on the roof of San Lorenzo Hospital and stared out over a vast expanse of gray mud. ''Thousands of people are buried under there,'' he said. Pointing to a house-sized boulder, he added, ''My family is under there.'' Mr. Rojas was one of a handful who scrambled to high ground after the Nevada del Ruiz volcano erupted Wednesday night, setting off an avalanche of mud and rocks that roared through this sleeping town of 25,000.

IJust before the Geneva summit meeting, Defense Secretary Caspar W. Weinberger has sent President Reagan a letter urging him not to make any agreements involving two key aspects of arms control. Mr. Weinberger, who will not be attending the Geneva conference, asked the President to avoid a commitment not to undercut the unratified 1979 strategic arms treaty or one that would affirm a ''restrictive'' interpretation of the 1972 antiballistic-missile treaty. Such an interpretation, he said, would hurt Mr. Reagan's program to develop a defensive system against ballistic missiles. The program, the Strategic Defense Initiative, is popularly known as ''Star Wars.''

The Soviet Union, apparently in a gesture in advance of the summit meeting next week, today told the United States that it would give exit visas to some American citizens' spouses who for years have been denied permission to leave, State Department officials said today. One official said the Foreign Ministry had provided a list of 10 names to the United States Embassy in Moscow. Eight of them are separated from their spouses, one was described only as a member of a divided family and another was described as a ''longstanding dual-national case.'' A State Department spokesman said, ''If these cases are indeed resolved as a result of these assurances, we would view this as a welcome step.''

Rescue workers struggled today with the immense task of saving survivors and recovering thousands of bodies from the sea of mud that destroyed this town and severely damaged 13 communities after the eruption Wednesday of a long-dormant volcano. The Government said tonight that 21,559 people were dead or missing in Armero and the other communities around the Nevada del Ruiz volcano. Officials said they had counted 1,433 injured so far, but this figure was expected to rise. 'Don't Have the Help We Need' Raul Alferez, a 20-year-old volunteer Red Cross worker who was leading the rescue operation here, said that while there were reports that tons of emergency equipment and supplies were pouring into Colombia, the material had not yet reached Armero, a town of 25,000, which was hardest hit. ''We don't have the help we need,'' he said, standing to one side of a roped-off square of grass that serves as the main aid station here. ''We need people and we need equipment. We need more helicopters and we need stretchers, gauze, anesthetics, all kinds of first-aid equipment.''

The National Broadcasting Company is planning to move its headquarters from the RCA Building, which it has occupied for more than a half century, company and city officials said yesterday. The officials said the network was reviewing several proposals in Manhattan and at least one in New Jersey to meet its need for more space and more modern studios. The network, whose current leases at Rockefeller Center begin to expire in 1989 and end entirely in 1997, is expected to decide on a new site by next February. An NBC spokesman, Curt Block, said that a move had been under study by a task force for several years and that active discussion of sites had begun about a year ago.

The Reagan Administration and some members of the Honduran Government often portray the Nicaraguan guerrilla army massed near this border town as a necessary buffer and a legitimate weapon against the Sandinista Government in Managua. But the Honduran coffee farmers who cut a hardscrabble existence out of the mountain valleys that stretch along the isolated frontier have a different view. They say the Nicaraguan rebels gathered in nearby camps represent a physical menace that has brought them economic ruin. After enduring the guerrillas' growing presence for the last four years, the farmers have decided to make their displeasure public. Two weeks ago, they sent a delegation to protest to the United States Embassy and to the Honduran Congress. They say they want the rebels to clear out.

A bomb seriously damaged the national headquarters of the Colombian Communist Party today, but no one was wounded, the police said.

A former Gestapo leader high on the list of wanted Nazi war criminals has been arrested in Argentina on a special extradition warrant from West Germany, Argentine officials reported yesterday. They identified the man as Walter Kutschmann, a 71-year-old businessman who has been living in Argentina since 1947 under the name of Pedro Ricardo Olmo. West German prosecutors, who had first sought his extradition nearly 15 years ago before dropping the effort, said he was wanted for the killings of Jews and other civilians in Poland during World War II. If an Argentine judge approves the extradition, Mr. Kutschmann would apparently be the first Nazi fugitive ever handed over by Argentina. Under previous Governments, Argentina was a favorite refuge for officials of Hitler's Third Reich.

In the first elections since civilian government returned here last March, about 18 million Brazilians voted today in elections to pick the mayors of 201 cities, including all state capitals and urban centers. The elections, which were hotly disputed - the Army was called in to patrol five cities - will measure the strength of the 5 old and the 25 new parties that are scrambling to fill the political vacuum left by the end of two decades of military rule. The Brazilian Democratic Movement Party, the dominant partner in the governing coalition, is expected to win in most of Brazil's 23 state capitals.

Prime Minister Shimon Peres served notice today that any member of the Cabinet who slanders the Government will be summarily dismissed. He issued the warning to Yitzhak Shamir, the Likud leader and Deputy Prime Minister, at a meeting in Jerusalem to terminate a crisis that grew out of unusually sharp denunciations of Mr. Peres's leadership by Ariel Sharon, the Minister of Industry and Commerce.

The United Arab Emirates announced today that it was establishing diplomatic relations with the Soviet Union.