What was going on when I was born?

With tensions running high after the assassinations of seven military men and Civil Guards in less than a week, Prime Minister Leopoldo Calvo Sotelo tonight accused unidentified foreign states of fomenting terrorism in Spain. In a television address to the country, the Prime Minister promised a ''long and hard struggle'' against terrorism, though he announced no new measures. At the outset of his talk, Mr. Calvo Sotelo, who heads a centerright Government, affirmed that ''terrorism in Spain cannot be understood only in terms of its internal traits, but also must be seen in the field of international action.''

Two children were fatally crushed yesterday morning by a 12-wheel tractor trailer as their mother was walking them and their baby brother across Seventh Avenue South opposite St. Vincent's Hospital on 11th Street. The crosswalk is part of a busy six-street intersection in Greenwich Village where traffic is usually heavy. The parents of children at nearby Public School 41 say they have been demanding a crossing guard for the intersection since September. According to the police and witnesses, the mother, Fatima Delosevic, and her three children began crossing the avenue from west to east at about 10:15 A.M.The truck, headed south on Seventh Avenue, had stopped for a red light. When it started again, it ran over the two older children, nearly crushed a baby carriage and caught one of the mother's shoes under a wheel before coming to a halt.

Syria today formally rejected Israeli demands for withdrawal of antiaircraft missiles from Lebanon as Philip C. Habib, the special American envoy, began discussions here on easing the crisis. ''Air defenses, including missiles, are part of Syria's armed forces,'' said a statement issued in Damascus by the Syrian Defense Ministry. ''They exist now, and will in the future, wherever Syrian troops are, when they need them.''

The Metropolitan Transportation Authority yesterday rejected a proposal that would have barred the use of air-conditioning on New York City buses unless the outdoor temperature exceeded 90 degrees. It said it would continue to leave such decisions ''to the discretion of the drivers.'' But some bus drivers may not have much of a choice. John D. Simpson, president of the New York City Transit Authority, said that on ''at least 2,200'' - or three-quarters - of the system's 2,700 buses equipped with air-conditioning, the equipment was not working at this time.

The Senate reversed itself today and voted, 49 to 42, to recommend a $7.9 billion reduction in cost-of-living increases for Social Security recipients and retired Federal employees in the fiscal year 1982. The saving would occur because of a change in the method of calculating increases in retirement benefits based on inflation. The Senate Budget Committee had recommended, and the Senate agreed today, that the increases should be based on either the Consumer Price Index or the national average increase in wages, whichever was lower, rather than solely on the price index. The Congressional Budget Office feels that the Consumer Price Index, because of the factors that go into its calculation, shows an unrealistically high rate of inflation. In recent years average wage increases have been lower than the cost-of-living increase as measured by the Consumer Price Index. The effect of today's vote to use the wage standard in calculating retirement benefits, combined with a proposed three-month delay next year in the date for the costof-living adjustment for retired Federal employees, would lead to an estimated saving of $7.9 billion next year.

The upward trend in the Government's index of producer prices for finished goods moderated in April because of smaller rises for food, gasoline and heating oil, the Bureau of Labor Statistics reported today. The index, which measures price changes for a broad array of goods sold to retailers, rose by eight-tenths of 1 percent last month, a decidedly smaller increase than March's 1.3 percent and in line with the January and February rises. In another report, the Labor Department said the nation's unemployment rate in April stayed at 7.3 percent for the third consecutive month. The figures were regarded as mildly optimistic since the economy generated about half a million additional jobs while the number of Americans out of work declined, though by an insignificant amount. (Page 9.)

The presidential election campaign wound up today in a thoroughly bad temper. The pressures of a race in which almost precisely half of the electorate seems ready to vote Sunday against the other half have told heavily on the equanimity of both President Valery Giscard d'Estaing and Francois Mitterrand, the Socialist candidate. Two private polls taken in the last three days showed Mr. Mitterrand ahead by three to four points but indicated that Mr. Giscard d'Estaing was narrowing the gap. A third, commissioned by the Giscard d'Estaing organization, gave the President a two-point lead.

Fresh from his budget victory in the House of Representatives, President Reagan ''is not talking compromise now'' on his tax-cut proposal, a key aide says, although top Congressional Republicans suggest privately that he will probably have to compromise later. The aide, James A. Baker 3d, the White House chief of staff, said that after yesterday's budget vote, the President felt that Congressional Democrats ''are moving toward him.'' Mr. Baker indicated that over the next month, the Administration would mount a strong effort to build broader public support for its tax program. But Mr. Baker did not categorically rule out the possibility of compromise by the time tax legislation reaches the House floor for a critical vote, probably in the second half of June. ''The President's not talking compromise now,'' Mr. Baker said. ''He's not at that point. He's not in the posture of actively seeking compromise. But he's willing to listen if someone makes a proposal to him.''

When the fighters show up and ask for some beans, some corn or some tortillas in this highland area, the Indian inhabitants have two choices. One is to give food to the callers, who are dressed in rollbrimmed straw sombreros, rude leather sandals and tattered trousers, discover that they are army troops in guerrilla disguise and be killed for helping the wrong side. The other choice is to not give food to them, discover that they really are guerrillas and be killed for helping the wrong side. The Indians who make up more than half of Guatemala's population of about seven million are caught in the middle of the violent conflict here. How they decide to get out of it could be the deciding factor in the outcome.

A dispute over how and when to begin lowering Sweden's high income tax rates led today to the fall of the coalition Government of Prime Minister Thorbjorn Falldin. The Government, which had governed for 20 months with only a onevote majority in Parliament, began to disintegrate Monday when the conservative Moderate Party withdrew from the Cabinet, charging that its two coalition partners had gone back on their pledge of a ''sweeping tax reform to aid economic recovery.''

TERRE, Guadeloupe, May 8 (UPI) - A bomb wrecked the local election campaign office of President Valery Giscard d'Estaing of France today, wounding two policemen and a civil servant, the authorities in the French Caribbean islands reported. A bomb, apparently planted by anti-French nationalists, exploded at Pointe-a-Pitre, Guadeloupe, last December during Mr. Giscard d'Estaing's visit there.

Nicaragua, anxious to avoid an open break with Washington, has asked President Jose Lopez Portillo of Mexico to take up the crisis in United States-Nicaraguan relations when he meets with President Reagan in Washington early next month. In an interview shortly before ending a state visit to Mexico today, Daniel Ortega Saavedra, coordinator of Nicaragua's junta, said that Mr. Lopez Portillo was willing to help Nicaragua improve its relations with the United States. ''It is easy to understand why Mexico should be inclined to echo our worries,'' he said. ''Mexico is seriously interested in trying to promote stability in the region.''