What was going on when I was born?

THE decision to buy an old or historic house used to be the beginning of a sentimental, rather than practical, odyssey. Buyers went ahead, regardless of the potential maintenance headaches, because they were captivated by the house's charm and by legends of generations past that seemed to permeate every creaky stair and beam. They did not expect any help with their problems, nor did they expect to have anyone tell them what they could or could not do to the house. Today, however, the purchase of such a house is becoming more and more like taking in trust a little bit of the national treasure. The house is now likely to be in an historic district, and buyers should be aware that such a designation is not simply honorific. It comes with legally binding restrictions and responsibilities in addition to very tangible benefits rarely available to owners of these properties before.

Chad ChallengePuts the FrenchIn a Testy MoodDispatching French troops to prop up a former African colony was bound to be awkward for Fran,cois Mitterrand, a Socialist President who had castigated his predecessors for doing just that. So last week, as several thousand French paratroops flew into Chad and the neighboring Central African Republic, Mr. Mitterrand loudly changed the subject. He authorized the newspaper Le Monde to portray him as staunchly resisting purported pressure from Washington. Mr. Mitterrand was acting only to rescue Africans from heavy-handed American tactics that threatened to create a dangerous new East-West battlefront, the paper said. President Reagan had sent so many messages, added Le Monde, that Mr. Mitterrand hadn't bothered to answer them all.

LUGANO, Switzerland The most spectacular exhibition in Europe this summer is not in Paris or London or Berlin but in a villa on the eastern tip of Lugano, Switzerland. In exchange for a loan of 40 paintings from his celebrated Old Master collection, Baron Hans Heinrich Thyssen-Bornemisza has borrowed 40 late 19th- and early 20th-century French paintings of the highest quality from the Hermitage Museum in Leningrad and the Pushkin Museum in Moscow. The show is of particular interest, since the paintings have been rarely seen in the West since they were acquired by the two great Russian collectors, Ivan Morozov and Sergei Shchukin, in the years prior to World War I. This Impressionism to Cubism greatest-hits shows, installed in the private quarters of the baron's Villa Favorita, the building that houses his Old Master museum, continues through Oct. 15. The Soviet authorities' selection of the baron's top 40, which includes paintings by Rogier van der Weyden, Titian, El Greco and Goya, will be on display at the Pushkin from Sept. 12 to Nov. 14 and the Hermitage from Nov. 19 to Feb. 1, 1984.

Chad ChallengePuts the FrenchIn a Testy MoodDispatching French troops to prop up a former African colony was bound to be awkward for Francois Mitterrand, a Socialist President who had castigated his predecessors for doing just that. So last week, as several thousand French paratroops flew into Chad and the neighboring Central African Republic, Mr. Mitterrand loudly changed the subject. He authorized the newspaper Le Monde to portray him as staunchly resisting purported pressure from Washington. Mr. Mitterrand was acting only to rescue Africans from heavy-handed American tactics that threatened to create a dangerous new East-West battlefront, the paper said. President Reagan had sent so many messages, added Le Monde, that Mr. Mitterrand hadn't bothered to answer them all.

There were cheers again at Giants Stadium tonight for Lawrence Taylor, boos for Scott Brunner and Phil Simms, and then Jeff Rutledge further confused the Giants' quarterback situation with a fine fourth-quarter performance as the Giants defeated the Baltimore Colts, 27-14, in an exhibition game. ''I'm not going to have an answer tonight,'' said Bill Parcells, the undefeated head coach. He raised his winning streak to three but still is not sure who will be his starting quarterback when the National Football League regular season opens in two weeks. Parcells was also not sure who his place-kicker would be after Joe Danelo kicked himself back into contention by hitting field goals of 42 and 40 yards into gusty, swirling winds. Meanwhile, Ali Haji-Sheikh, the rookie who had apparently taken the lead for the job with five field goals a week ago, missed his only attempt, a 36-yarder.

Wall Street Guessing Game Divining what credit course the Federal Open Market Committee will chart at its next meeting is a popular Wall Street ritual. The policy-making arm of the Federal Reserve convenes in Washington on Tuesday, as it does every six weeks. And the message analysts read in their crystal balls is that Fed policy - and hence interest rates - will remain unchanged. In May the panel decided to tighten the availability of credit for the first time this year, and that sparked higher rates. There has been further tightening since then, but with money supply growth slowed for the past two weeks, the inflation incentive to tighten again should be lessened.

A dramatic increase in the interstate shipment of highly radioactive spent nuclear fuel rods by private carriers is under way after years of relative inactivity. Because of a Federal court order, utilities plan to send hundreds of truckloads of the nuclear wastes in the next few weeks from an outmoded reprocessing plant in West Valley, N.Y., back to the Eastern and Middle Western power plants that originated them. In addition, because of limited storage at some nuclear plants and extra space at others, the General Electric Company has begun shipping hundreds of tons of the rods from one site to another, using Morris, Ill., as a crossroads and prompting particular concern in that state. Shipments by private carriers began in the mid-1960's but had become infrequent in recent years because of legal maneuvers and a lack of commercial storage facilities. However, it appears they will be increasing rapidly because of Federal court rulings.

President Mobutu Sese Seko of Zaire paid an unexpected visit here today as the Chadian Government charged that Libya was preparing to make new military advances toward the south. ''I have come to show that Chad does not stand alone,'' said President Mobutu, who has sent more than 2,000 troops to support the Chadian Government in its battle against Libyan-backed insurgents. Western diplomats confirmed estimates from Washington this week that Libya's strength south of an area that Col. Muammar el-Qaddafi, the Libyan leader, annexed a decade ago, now stood at 3,000 to 3,500 troops. The figure quoted by the same sources last week was 2,000 to 2,500 Libyans in support of rebels loyal to former President Goukouni Oueddei.

ALTHOUGH alcoholism has become more accepted as an illness, with ballplayers, actors and other public figures acknowledging their addiction, there still is often a stigma attached to those who admit that they are alcoholics. For that reason, the year-old alcohol-detoxification unit of Yonkers General Hospital emphasizes confidentiality. ''We call it a Special Program Unit,'' said Michael Feinman, associate administrator of the hospital. ''This reduces the possibility of the stigma of alcoholism. Even though Yonkers is the fourth-largest city in the state, it's really a small town in many ways.''

TO the untutored eye, a rock is a rock. And while the rock that remained in the bottom of Carol Traynor's sieve looked like the other rocks she had found that day in a virgin oak forest deep in the Mashomack Preserve, she soon realized that she had uncovered something unusual. Mrs. Traynor, a graduate student in anthropology at the State University at Stony Brook who enrolled in a special five-week summer course, had come to the Nature Conservancy preserve on Shelter Island to help survey its 2,000 acres for the university's Long Island Archeological Project. The aim of the project is to piece together a scientific portrait of the region's past, and Mrs. Traynor guessed that the rock in her sieve had a place in that historic jigsaw puzzle. ''I just knew that it was a flake, a quartzite flake hacked off a larger stone,'' she said, still excited even days after her discovery.

-brick townhouse on East 55th Street, Allied Bank International looks solidly prosperous. But beneath the elegant facade, it has been badly shaken. Indeed, the bank consortium would have failed if its 12 often contentious shareholders - all large regional banks in the United States - had not agreed earlier this year to ante up more than $300 million - or about 40 percent of Allied's total assets - to keep it solvent. Its problem is that almost 30 percent of its loans are to debt-ridden countries in Latin America - 9.8 percent to Mexico alone. Last year, the commercial bank reported a loss of nearly $19 million as a direct result of problem loans to that region.

The quest was successful, and earlier this month Cadwalader acquired two adjoining and interconnecting buildings, a 10-story structure at 100 Maiden Lane and the 16-story building next door at 102 Maiden Lane. The price was $20 million.