What was going on when I was born?

Unemployment in April rose to 9.4 percent of the labor force, the highest level in 40 years, largely because of layoffs in manufacturing industries and a decline in retail jobs, the Labor Department reported today. In reporting an increase of four-tenths of a percentage point in the unemployment rate last month, the Bureau of Labor Statistics said that 10,307,000 people were jobless in April, an increase of 450,000 over March. The bureau found more than 99,340,000 people still employed, but this was 152,000 fewer than a month ago. In New York, the state unemployment rate dropped from 8.2 percent in March to 8.1 percent in April, while the New York City rate dropped sharply to 9.1 percent from a 12-month high of 10.1 percent in March. (Page 9.)

The news of the jump in the unemployment rate comes at a time when the Reagan Administration, the financial markets and a large majority of economists have begun to forecast an upturn in the business cycle. They say the upturn should come either in the current April-June quarter or, at the latest, in the next quarter, following the scheduled 10 percent cut in personal income taxes next July 1. The rise in the unemployment rate to 9.4 percent could make those forecasters somewhat more cautious. James Capra, an industrial economist at the New York Federal Reserve Bank, said: ''It is not a good situation. Not many forecasters had the unemployment rate topping out as high as 10 percent, but with this jump it could happen.''

In an effort to protect its task force in the South Atlantic and to increase military pressure on Argentina, Britain announced tonight that it would treat as hostile any Argentine warship or plane found more than 12 miles from the mainland coast. In effect, the declaration constituted a warning to Argentina to keep its planes at their bases and its ships in port or face attack. It extends the territory covered by the air and sea blockade imposed in a 200-mile zone around the Falkland Islands on April 30, vastly increasing the area to be patrolled by the British fleet's ships and planes. The Argentine coastline extends for about 2,500 miles. Argentina Dismisses Move Defense Minister Amadeo Frugoli said Argentina would respond to what he called growing aggression by Britain, and Argentine naval officers said the British fleet in the South Atlantic did not have the power to enforce the extension of the blockade around the Falklands. (Page 4.)

A senior State Department official said today that the United States felt that unless Argentina agreed soon to withdraw its forces from the Falkland Islands, Britain would invade the islands ''and prevail in the end.'' In a briefing for a few reporters, the official said the United States, despite backing Britain in the dispute, was still hopeful of avoiding what he called ''more terrible fighting.'' But he said Washington was frustrated by Argentina's refusal to accept any formula for a settlement that called for a withdrawal of Argentine troops without a guarantee in advance of Argentine sovereignty over the islands. At the United Nations, Secretary General Javier Perez de Cuellar said he had perhaps two days to achieve a cease-fire that would be acceptable to both Argentina and Britain. (Page 5.)

The Supreme Court today turned down, without comment, the appeal by RKO General Inc. of the Federal Communications Commission's decision to strip the company of its right to operate a highly profitable Boston television station. The F.C.C.'s action was upheld last year by the United States Court of Appeals here. Permission to operate WNAC-TV, which broadcasts on Channel 7 in Boston, is now expected to go to the New England Television Corporation. Under a former corporate identity, that company has been challenging RKO's Boston license since 1968.

Claus von Bulow was sentenced to 30 years in prison today for twice trying to murder his wife. He left the courtroom under bail increased to $1 million from $500,000. Mr. von Bulow showed no expression as he was sentenced to 10 years in prison on the first count of attempted murder and 20 years on the second. The sentence would be served in the Adult Correctional Institution, at Cranston, R.I., an aging and overcrowded prison. Under Rhode Island law, Mr. von Bulow would have to serve 10 years before becoming eligible for parole.

President Reagan has decided to propose that the United States and the Soviet Union adopt a common ceiling of 850 intercontinental nuclear missiles with no more than 5,000 warheads on those missiles, according to Administration officials. Both sides would have to reduce the number of their missiles to get within the ceiling of 850 land-based and sea-based missiles. The Soviet Union now has about 2,350 and the United States 1,700. To comply with the ceiling of 5,000 missile warheads, the United States would have to cut some 2,200 warheads and the Soviet Union would have to destroy 1,300. The reductions would take place over five to 10 years.

Mayor Koch warned the city's private hospitals yesterday that they were closing their emergency rooms to too many ambulances carrying heart attack victims and seriously injured persons. The practice, he said, threatens ''the city's entire emergency medical system.'' Private hospitals have refused cardiac and other serious cases because, they say, their emergency rooms are overcrowded. The Mayor's warning was issued shortly after the Greater New York Hospital Association, an organization representing the city's private hospitals, advised its members to reduce the number of such closings.

Against the urgings of the Reagan Administration and in the face of strong opposition from some religious groups here, the Rev. Billy Graham arrived in the Soviet capital today to preach and to participate in a Kremlin-backed conference of religious leaders on nuclear arms control. The kisses that Mr. Graham exchanged at Sheremetyevo Airport with Soviet officials symbolized a landmark in the career of the 63-yearold American evangelist, who came here as a tourist in 1959 but who has never previously included the Soviet Union among the dozens of nations to which he has carried his religious message. With the warmth of the welcome in the V.I.P. lounge at the airport, the Soviet authorities seemed to signal that, for them, Mr. Graham was close to the ideal guest for the time. Before coming here, the evangelist turned aside appeals from Vice President Bush and other senior Administration officials who feared that he would be used for propaganda purposes at a time when the Administration has placed a chill on Soviet-American relations.

The South African Law Commission, a legal review panel, recommended to Parliament today that it pass legislation giving wives equal status with their husbands.

Iran said today that its troops had breached Iraqi lines and taken a 22-mile stretch of the southern Iran-Iraq border that the invaders had occupied since the first weeks of the war, which began in September 1980. Iraq's military command conceded that the Iranians had mounted ''a fresh offensive on all areas of operation'' in the south but said the Iranian attack had been contained. ''Fierce fighting is raging with all kinds of weapons and planes,'' the Iraqi command added. The battle area was said to stretch from the northern outskirts of the Iranian oil port of Khurramshahr, which was still held by Iraq, north to Hosseinieh. Iran said its troops had recaptured more than 100 square miles of territory.

Vice President Bush was welcomed by the Chinese leadership today and was immediately told that ''serious obstacles'' over Taiwan were obstructing the development of Chinese-American relations. Mr. Bush arrived here this morning from Hangzhou, his initial stop in China. He spent Thursday in the eastern resort city resting and being briefed in preparation for his talks in Peking. This afternoon the Vice President was greeted by Deputy Prime Minister Wan Li at the Great Hall of the People, where he talked for two hours with Foreign Minister Huang Hua.