What was going on when I was born?

A State Supreme Court justice, ruling in a New York City case, yesterday upheld efforts by advocates for the homeless to enforce supervision for thousands of young people between the ages of 18 and 21 who leave foster care. Although state law requires supervision under the foster-care system for people up to age 21, the judge found that the city had failed to provide adequate care beyond age 18. At that age, those in foster care are free to leave the program. In the case yesterday, Justice Elliott J. Wilk in Manhattan wrote that six young people between 18 and 21 who were discharged from foster care and subsequently became homeless must be allowed to return to such care or be provided some other form of supervision. Justice Wilk found that these six people had been discharged from foster care by the city before they were ready.

El Salvador's Air Force has come to play an essential role in the Government's war against leftist rebel forces and has almost doubled in size in the last year, according to both United States and Salvadoran officials. The number of bombs and rockets used in combat is increasing, and American-provided helicopter and AC-47 gunships are now commonly deployed against guerrilla units. Some Western officials contend that the army might have lost the war without the sharply increased air power provided by the United States in recent years, especially a new fleet of helicopters used to place troops rapidly in rebel areas. Used in Rebel Strongholds In the last year, the air force appears to have used its new muscle mostly in concentrated attacks on areas regarded by the Government as guerrilla strongholds. Such attacks have become the focus of criticism of the Salvadoran Government. Several human-rights organizations have accused the Salvadoran Air Force of bombing civilians in guerrilla areas and of trying to drive rebel supporters into refugee camps.

The BankAmerica Corporation, the nation's largest bank company after Citicorp, stunned the financial world yesterday by announcing that it lost $338 million in the second quarter. The loss was one of the largest in banking history, and appeared to reflect pressure by Federal regulators on banks to bolster their reserves against the possibility of loans going bad, even at the cost of a drop in profits. The loss was caused by an extraordinary $892 million addition to these loan-loss reserves, which now total $1.5 billion. Bank analysts said the addition had been made under pressure from regulators.

''I've never known anyone from Tennessee who wanted to retire to New York.''

Alma H. Johnson, her hair shot through with gray, stood on her stoop on Yates Road in South Jamaica and surveyed the midafternoon activity. She muttered disapprovingly about an illegal curbside car repair business and chastised a little girl playing near a recently purchased home. ''Teresa, don't be hitting a ball on that house anymore,'' Mrs. Johnson said. ''It belongs to somebody.'' ''They all know me,'' Mrs. Johnson said of the neighborhood children. ''When I see them do something that's not right I try to correct them, teach them morality and respect for other people.''

Pushing further into record territory, the stock market yesterday registered its second consecutive big gain as investors cheered the Federal Reserve's decision to raise its targets for money supply growth. The Fed's action, announced after the market closed on Tuesday, allayed fears that recent increases in the money supply might cause a tightening of credit conditions. With institutions scrambling to participate, volume soared yesterday to 159.9 million shares, the fourth-busiest session of 1985 and the heaviest since 170 million shares traded on Jan. 30. Scoring a double-digit gain for the second consecutive day, the Dow Jones industrial average jumped 10.08 points, to 1,357.97. The index of 30 high-capitalization stocks had gained 12.43 points on Tuesday.

The debate over the timing of President Reagan's cancer treatment intensified today when a doctor who examined Mr. Reagan said his medical team had recommended in March that the President receive a thorough examination of his colon as soon as possible. But the White House contended that there was no recommendation of urgency for such a colonoscopic examination in the written report submitted by the military doctors who examined the President. Mr. Reagan did not receive a colonoscopic examination of his large intestine until last Friday, at which time surgeons at Bethesda Naval Medical Center discovered a polyp that proved to be cancerous. White House Defends Decision Since that time, the question of whether the colonoscopy and surgery should have been performed last March has been debated among physicians. Today, Larry Speakes, the White House spokesman, defended the decision not to conduct a colonoscopy until this month, and he strongly denied that White House physicians had ignored warnings that they should have acted sooner. He also defended the White House's efforts to limit interviews with the President's doctors. [Page A14.] In another sign of the intensifying debate over Mr. Reagan's medical care, a vice president of the American Cancer Society said Mr. Reagan's physicians had misinterpreted the society's guidelines for when extensive testing should be conducted to look for polyps in the colon.

Elizabeth Wanjara heard about the Decade for Women Conference on a transistor radio at her home in the town of Bungoma in western Kenya, 450 miles from here. With eight local women, she saved up by selling honey and knitting sweaters and bought herself a bus ticket. Mrs. Wanjara doesn't know exactly how old she is or how many grandchildren she has. She speaks only her tribal Kiswahili dialect and cannot read or write.

Companies BankAmerica reported a $338 million loss for the second quarter, one of the largest in banking history. The loss appeared to reflect pressure by regulators for banks to bolster their reserves against the possibility of loans going bad, even at the cost of a drop in profits. The banking company added $892 million to its loan loss reserves and wrote off $382 million in loans. [D1.] A.T.&T. earnings rose only 1.3 percent in the latest quarter, to $461 million, on slightly lower revenues. Analysts said A.T.&T. is not cutting costs as quickly as prices are falling on many of its products. MCI's profit rose 3.9 percent, to $34.3 million, while Bell Atlantic rose 14.7 percent, to $283 million. [D1.]

The American Telephone and Telegraph Company said yesterday that earnings rose only 1.3 percent in the quarter ended June 30, to $461 million, from $455 million. Revenues declined, to $8.55 billion, from $8.58 billion. Per-share earnings also dropped, to 41 cents, from 43 cents, although there were more shares outstanding in this year's second quarter than last year's. Wall Street analysts said the A.T.&T. report amounted to bittersweet news from the phone giant. Unit sales of switchboards, phones and other communications equipment are running well ahead of company expectations, they noted. The company is also holding its own in the battle for long-distance customers. But A.T.&T. is not cutting costs as quickly as prices are falling on many of its products, the analysts said.

International Israel rejected a list of Palestinians whom Yasir Arafat has suggested as possible members of a Jordanian-Palestinian delegation that could hold preparatory peace talks with Washington, which had submitted the list to Israel. [Page A1, Column 2.] El Salvador's Air Force has come to play an increasingly essential role in the Government's war against leftist guerrilla forces and has almost doubled in size in the last year, according to United States and Salvadoran officials. [A1:3.]

When the Federal Reserve Board broke the back of inflation in 1982, Paul A. Volcker, its chairman, performed his own brand of financial wizardry by encouraging his fellow board members to keep a tight rein on the money supply when the economy cried out for more. Now he is apparently determined to fight a new public enemy - the trade deficit - by keeping a loose grip on the money reins and fostering low interest rates. The Fed has jettisoned its old target for money supply growth in favor of a new, more generous target and has accepted the risk that its old nemesis, inflation, could become stronger in the future. The change in the money supply growth target, to accept the rapid growth in the first half and still keep a ceiling in sight, was widely seen by economists as a way for the central bank to show that it remains serious about fighting inflation and, at the same time, continue to stimulate the economy by keeping interest rates low. In his testimony before Congress yesterday, Mr. Volcker maintained that the Fed's new policy could accomplish its task of stimulating the economy without reviving high inflation.