What was going on when I was born?

The Reagan Administration said today that it was ''prepared to facilitate'' efforts by the Rev. Jesse Jackson to win the release of five Americans who have been abducted in Lebanon. But it also repeated its firm opposition to meeting the demands of the terrorists holding the captives. ''If Jesse Jackson can do anything, that would be just fine,'' President Reagan said as he boarded his helicopter this afternoon for a weekend at Camp David. Although saying that it would put no obstacles in the way of a possible mission by Mr. Jackson and the families of some captives, the State Department made clear that the Administration was strongly opposed to meeting the conditions for their release set by the group called Islamic Holy War. The group says it is holding five Americans and two French diplomats at an undisclosed location or locations.

Equal employment rights for women, at least in theory, came to Japan today, but some people wondered whether this resolutely male-oriented society would even notice. Of the major industrial countries, Japan has been among the more resolute in keeping its men on the job and its women within reasonable proximity of the kitchen. After seven years of public debate and behind-the-scenes compromise, the Parliament gave final approval this afternoon to a bill encouraging employers, beginning next April, to end discrimination on the basis of sex in their hiring, assignment and promotion policies. Severe restrictions now placed on overtime and late-night work by women would be ended in many jobs. These limitations were sometimes characterized as privileges by people who wanted to retain them. But they have had the effect of keeping women out of many jobs.

President Reagan has decided that, under his tax revision proposal, only families with more than $70,000 of taxable income would be subject to the highest tax rate of 35 percent, a senior Administration official said today. The official added that the plan's lowest rate of 15 percent would apply up to about $30,000 of taxable income. The middle rate, 25 percent, would apply between $30,000 and $70,000, according to the Reagan adviser, who spoke on the condition that he not be identified. There are now more than a dozen tax rates, ranging from 11 percent to 50 percent. The official added that Mr. Reagan had ruled out an even lower maximum rate, despite continuing appeals from some members of Congress. The chief advocate of a lower top rate has been Representative Jack F. Kemp, Republican of upstate New York.

Health insurers will pay $450 million, far more than expected, to private and public hospitals in New York State over the next two years as part of a state-run program meant to contain hospital costs, according to state officials. The payments are subsidies established by the State Department of Health five years ago as an incentive for hospitals to curtail what the state said were unnecessary hospital stays. Drop in Hospitalization At the time, hospital costs were soaring, largely because of a steady increase in hospitalization. But for reasons unrelated to the state's subsidy program, hospitalization has been falling more sharply than expected.

Large increases in military spending have for many years failed to yield comparable increases in weapons delivered to the armed services, and some critics of Pentagon practices believe that basic changes are needed in the incentives that influence those who buy and make weapons. There seems to be a growing consensus among such critics that the way the Defense Department customarily does business is based on an inverted system of rewards and punishment. These incentives tend to reward, rather than penalize, cost increases in a tank or airplane. They also encourage uniformed procurement officers to place a far higher priority on gaining Congressional approval to begin a new weapon program, rather than on controlling prices. Values Are Entrenched The most often discussed remedies for the troubled system of acquiring weapons and equipment for the armed services are greater competition in the military industry, better preparation and supervision of contracts by officials and more realistic planning by the Pentagon.

The Federal Reserve, in a forceful step to support a flagging economy, approved a half-point cut in its lending rate today, to 7 1/2 percent. The new level is the lowest in almost seven years. Minutes after the Federal Reserve's announcement, Citibank and the Chase Manhattan Bank lowered their prime lending rates to 10 percent, from 10 1/2 percent. The prime-rate cut had been initiated Wednesday by the Bankers Trust Company. [Page 35.] The central bank said its action reflected stagnation in the manufacturing sector of the economy, which has been subject to severe competition from imports, and the fact that inflation is generally subdued. The vote was 5 to 0, with two governors absent.

A strike by United Airlines' pilots forced the cancellation of hundreds of flights yesterday at 89 airports. The degree of travel disruption varied. Talks between the 5,200-member union and the airline, the nation's largest, ended shortly after a Thursday midnight deadline in a stalemate over details of a two-tier wage scale under which newly hired pilots would receive lower pay than those now flying. United said late yesterday afternoon that it was trying to operate 11 percent of the day's scheduled flights, 165 of 1,577, with management pilots, of whom it has 200, and with some union members who defied their colleagues' picket lines.

The factories on this swampland have turned the nearby town into a place of superlatives: in Cubatao, pollutants in the rain have reached some of the highest levels known in the world; the air is considered unfit for humans on a record number of days, and more cases of cancer, stillbirths and deformed babies are reportedly recorded here than anywhere else in Brazil. Nearly 100,000 people live in this town on Brazil's south coast, under acrid layers of red, ocher and gray that trap the heat and hover in the sky. On days when the act of breathing becomes a challenge, the children and the aged are given emergency oxygen supplies. This huge petrochemical center, environmental experts fear, is an industrial disaster waiting to happen. They say enough accidents have occurred because of low safety standards and poor maintenance for their fear to be well founded.

An ''emotionally upset'' corporal opened fire on Tamil civilians at an army camp in Anuradhapura today, killing 6 people and wounding 16 before being shot to death by his commanding officer, the Government said. It was the latest incident in a wave of violence that has claimed the lives of more than 220 people, mostly civilians, in the last four days.

Sinn Fein, the political arm of the Irish Republican Army, has won seats on 17 of 26 district councils in local government elections in Northern Ireland. As of tonight, with all but two seats from the election decided, Sinn Fein had won 58 seats and 11.8 percent of the popular vote. The party ran 91 candidates in areas where it felt it might find strong support. Party leaders had said they would be happy with 35 seats.

President Jose Napoleon Duarte of El Salvador, after his discussions with President Reagan on Thursday, began a series of meetings and appearances today designed to demonstrate support from politicians and institutions in the United States. But Mr. Duarte's second day in Washington included criticism from labor leaders over the unsolved slayings of two American labor organizers and a Salvadoran land reform official in El Salvador in 1981. At a meeting with Mr. Duarte this morning, Lane Kirkland, president of the American Federation of Labor and Congress of Industrial Organizations, and William C. Doherty Jr., executive director of the American Institute for Free Labor Development, chided Mr. Duarte for the lack of progress in the case, Mr. Doherty said.

Pope John Paul II, commemorating those who died on the battlefields of Flanders, warned today against ''unilateral slogans'' and ''simple sentimentalism'' in the pursuit of peace. John Paul chose this town, surrounded by 170 war cemeteries, to call for peace while vigorously endorsing the right of nations to protect themselves. The Pope's statement represented one of his clearest defenses of Roman Catholicism's traditional ''just war'' teaching, which holds that the use of force can sometimes be justified. The address implicitly criticized a pacifist current in the church in recent years.