What was going on when I was born?

International A key foreign policy review is under way in the Reagan Administration, according to authoritative Administration officials. They said President Reagan was seeking a possible way to ease the economic sanctions imposed against Poland and the Soviet Union over the military crackdown in Poland, including a scaling back of the ban on equipment for the new natural gas pipeline from Siberia to Western Europe. (Page A1, Column 6.) Moscow warned Washington that it would shape its policy ''with due consideration'' of any dispatch of American troops as part of a multinational force to evacuate Palestinian guerrillas from west Beirut. The Soviet press agency Tass said the statement had been made by Leonid I. Brezhnev, the Soviet leader, in his latest letter to President Reagan. (A1:4.)

The Argentine defense on the Falkland Islands was undermined by poor leadership and corruption that left many soldiers sick and hungry and with faulty weapons, according to many of the returning soldiers. Soldiers who fought on the front lines said many of their officers had deserted them. Some told of demoralized fellow soldiers - most of them teen-age draftees with only a few months' service -shooting themselves in the foot in order to be withdrawn. As the accounts of the returning soldiers have spread, often repeated in interviews with the press, so have calls for an inquiry into the war. According to some soldiers, the army has tried to silence them by threatening them with dishonorable discharges or extended draft service if they talk to the press.

''In connection with statements to the effect that the United States is prepared in principle to send a contingent of American troops to Lebanon, L.I. Brezhnev warned the United States President that, if this really took place, the Soviet Union would build its policy with due consideration of this fact.'' - Statement by Tass, the Soviet Government's press agency. (A6:4.)

Leonid I. Brezhnev has sent a letter to President Reagan saying that, if the United States sent troops to Lebanon, the Soviet Union would ''build its policy with due consideration of that fact.'' Text of Tass announcement, page A6. The letter, reported today by Tass, the Soviet Government's press agency, was reportedly delivered in Washington Wednesday by Ambassador Anatoly F. Dobrynin. It was the latest of a series of exchanges on Lebanon between the Soviet and American leaders.

In an unexpected move, the New York City Opera announced yesterday a consolidation of its fall and spring seasons at the New York State Theater into one season extending from July until December. This will mean elimination of the traditional spring season as of 1983. Company officials stressed that the decision will not reduce the number of performances annually in New York City, but only rearrange those performances into one season. No plans have been announced for the company in the winter and spring months, or for the rental of the State Theater in March and April.

Last fall, when many contractors began expanding production to meet the demands of the Reagan Administration's increased military budget, the Secretary of Defense, Caspar W. Weinberger, sharply reduced the Fairchild Republic Corporation's one prime contract - a 10-year-old agreement to make the Air Force's A-10 Thunderbolt attack planes. Suddenly, the 51-year-old aerospace manufacturer, a subsidiary of Fairchild Industries, became ''a prime contractor with no prime contract,'' as one top executive put it. Within a few weeks the company laid off 1,000 employees - more than 10 percent of its assembly-line crew. But now Fairchild Republic, whose predecessor built more than 15,000 Republic P-47's during World War II and had five prime contracts in the 1950's, is back in the military business.

An article in Business Day yester- day incorrectly described the assets of Mego International Inc. Mego, along with its domestic subsidiary, the Mego Corporation, has approximately $21 million in assets.

The Federal Reserve Board gave the go-ahead yesterday for banking companies in one state to invest in the nonvoting stock of banks in other states. But the Fed issued strict regulations to assure that the purchasing bank would not gain control over the bank being acquired. Bankers predicted that the ruling would lead to a flood of proposals for such interstate mergers. They said the Federal Reserve felt obliged to issue guidelines because of the large number of inquiries it was receiving.

SUMER is icumen in, and that, as usual, means that music lovers are going out. It's hardly surprising. Even in this age of airconditioning and acoustic consultants, or perhaps because of it, there seems more eagerness than ever to put music and the great outdoors together. Outdoor concerts are as old as sound itself, of course, and despite the many tricks Mother Nature has found to frustrate human noisemaking when it invades her territory - everything from singing cuckoos to sudden squalls, lightnings, thunderings, murmurs and rustlings - the call of the wild endures. Something about a starry canopy brings out the animal in us as well, and it can be downright exciting to pit that part of ourselves against the sublime strains of Beethoven or Wagner - to satisfy both beauty and the beast - even with the choruses of chirping, buzzing, croaking and flapping that come as part of the scenery. This weekend finds the hills, not to mention the valleys, meadows, woodlands, parks and estates, alive with the sound of music. Many of America's summer festivals are in full swing, luring visitors to far and not-so-far-away spots for a rendezvous with rhythm, melody and harmony. For some, music may be the principal enticement; for others, it may simply be an adornment to nature, isolation or wilderness.

Prices rose sharply and interest rates fell in the credit markets as speculation mounted that the Federal Reserve Board has eased monetary policy. In extremely active trading, Treasury bill rates declined by more than half a point, while Treasury note and bond prices were higher by up to 2 points. Most of the gains came after the Fed arranged temporary purchases of Treasury bills. (Page D1.) Stock prices rose dramatically after the drop in rates became known. The Dow Jones industrial average was up 5.32 points, to 804.98, at the close after being off 10.09 points at 1 P.M. (D6.) Assets of money market funds rose $944.3 million in the week ended Wednesday. (D9.) The dollar fell, while gold prices rose $10.75 an ounce, to $321.50, in New York. (D10.) Commodity futures rallied. (D10.)

The army's Deputy Chief of Staff said today that Israeli forces in Lebanon were making logistical preparations to stay through the winter if necessary. Speaking in an interview on the army radio, the officer, Maj. Gen. Moshe Levy, stressed that the preparations were not necessarily indications of intention but that the possibility of a long-term deployment had to be taken into account in planning. Another station, the Israeli radio, reported that the army was building new paved roads, moving bases from hilly to flat terrain and installing water pipes. It said the army was building a prison camp for Palestinian detainees near Nabatiye in Lebanon, with barbed-wire fences, guard towers and earthen walls. Israel has taken nearly 6,000 prisoners during the war, many of them from third countries.

ATLANTIC CITY THIS recently reborn resort teems with people on a summer weekend, but so many of them are in the casinos that visitors not interested in gambling have plenty of room to maneuver on the oceanfront strip. And because noncasino enterprises have accompanied the casino boom, the opportunities to feel royally wined, dined and entertained are considerable -even if you ignore the casinos entirely. While visitors who haven't been to Atlantic City recently may be surprised to see that the boom has done little to improve the city proper, the four-mile Boardwalk is still a comfortable ocean veranda, now marked by some elegant shops in the Boardwalk hotels. By day, the beach and Boardwalk still invite strolling, sunning and swimming. And some of the long-familiar Boardwalk piers remain open, with Steeplechase Pier still offering merry-go-round, roller-coaster and other rides and Central Pier's sky needle providing a bird's-eye view of the resort.