What was going on when I was born?

The International Harvester Company, which recently avoided default by negotiating an agreement with its lenders, said failure to reverse its declining sales in the next few months could force it to file a bankruptcy petition. Harvester acknowledged in a statement filed this week with the Securities and Exchange Commission that it had been losing its customary share of the truck and farm tractor markets, both severely depressed. It said its survival depended on ''significant'' improvements in these markets.

Seen from this Iraqi border command post 170 miles southeast of Baghdad, the front was mostly quiet. A small wood that was said to shelter Iranian troops two and a half miles away could be seen through field glasses. There had been some sporadic fighting to the north in the morning, and an occasional shell was still being fired by Iraqi gunners. There was no reply from the Iranians, who, according to Iraqi officers, were short of ammunition.

President Reagan was told that the G.O.P. lacks the votes in the House to advance the 1983 tax cut by six months. Congressional leaders said they expect Congress to demand cuts in the proposed arms budget and to reject further cuts in social programs. (Page A1.) Martin S. Feldstein, Mr. Reagan's chief economic adviser, told him that a highway repair plan urged as a way to create jobs might actually cost jobs. (D16.) Leaders of the steelworkers have approved major concessions, including a $2.25 an hour cut in wages and benefits, according to union and company sources. In return, they said, the companies have offered workers a share in their profits. Locals vote today on the plan. (A1.) The U.A.W. and Chrysler will resume talks soon in the dispute that led to a strike in Canada. (D16.)

Argentina's central bank, in a major restructuring of part of the nation's crushing foreign debt, announced today that it was substituting five-year bonds and promissory notes for $4.7 billion in debt that private concerns must repay foreign creditors over the next six months. The central bank declared that it would not begin paying back the principal on the bonds and notes until the fifth year. It said, however, that it would pay interest every six months. The move, in effect, means the private debtors will repay the principal owed to foreign banks with Government bonds rather than with cash. The dollar-denominated bonds will only be negotiable abroad.

IT would seem a normal weekend in New York's musical heartland. Tonight, the Sylvan Wind Quintet is playing Ravel and Rossini and the Wond'rous Machine is singing ensemble music by Byrd, Lassus and Palestrina. Tomorrow in Brooklyn, there's Boito's opera ''Mefistofele'' and not far away a 40-piece orchestra playing Haydn and Mozart. Sunday, Lynne Aspnes plays her harp on Manhattan's Upper West Side and not far from there the Bach series called ''Evenings With Johann S.'' continues. Typical events, certainly, except for one thing - all of them are taking place in churches. Places of worship are bulging with music, much of it secular. It is a symbiotic coming together - where the aspirations of musicians, many young and in need, meet the aspirations of New York's churches. The Sylvan Wind is playing at St. Peter's Lutheran Church - known also for its jazz -in the Citicorp Center, Lexington Avenue and 54th Street, at 8 tonight. At the same time the Wond'rous Machine is singing in St. Ignatius's Episcopal Church, West End Avenue and 87th Street. ''Mefistofele,'' which is also part of the Metropolitan Opera's repertory this season, is being presented by the Brooklyn Opera Society tomorrow night at 8 in the Episcopal Church of St. Ann and the Holy Trinity, Clinton and Montague Streets, in Brooklyn Heights. And also at that time, the Haydn-Mozart Chamber Orchestra will be at St. James Roman Catholic Cathedral, 250 Cathedral Place in Brooklyn.

''The Soviet Union has been and is for normal, and even better, friendly relations with the United States of America.

New York State's 190,000 employees will pay 10 percent of health insurance premiums for individual coverage under a major restructuring of the state's health insurance program, the state's Director of Employee Relations said yesterday. The state had formerly paid the full cost. The director, Meyer S. Frucher, said that the cost-sharing and other changes would produce savings of $142 million over the next two and a quarter years. He described the new arrangement as a landmark step at a time of reduced state revenues and rising health costs.

If all goes according to plan, 17-year-old Miguel Vazquez will fly from a trapeze into the hands of a catcher today, completing four full turns at 80 miles an hour on the way and thus repeating his recent feat as the first human known to have successfully performed a quadruple somersault. The Mexican-born Flying Vazquez family is a highlight of the Ringling Bros. and Barnum & Bailey Circus, running through Nov. 28 at the Byrne Meadowlands Arena in East Rutherford, N.J. It's about 10 minutes from the Lincoln Tunnel; buses from the Port Authority go there frequently. Today's shows at 10:30 A.M. and 7:30 P.M. Tickets are $6 to $9.50 and may be purchased through Chargit, 944-9300, or Ticketron offices. Information: (201) 935-8500. TRIBAL ARTS ON PARADE In the market for an Ashanti fertility statue? A royal robe? A Zulu loincloth? These and other tribal handicrafts - including baskets, pottery, musical instruments, dance masks and antique jewelry - are on sale during a festival going on through Sunday at the Tribal Arts Gallery, 84 East 10th Street. There will be puppet performances and demonstrations of mask-making, weaving and an African game called Owarri. Admission is free. Information: 982-4556.

Because of a transmission error, a dispatch from Moscow yesterday about Soviet-American trade incorrectly quoted Arthur A. Hartman, the United States Ambassador. He said the United States would not relent in its determination to link trade issues to ''our overall political relationship'' with the Soviet Union.

The executive board of the United Steelworkers of America approved a tentative agreement yesterday that calls for a cut of about 10 percent in wages and benefits and other major concessions, according to union and company officials. The concessions underscored the depressed state of the steel industry, which is operating at about 40 percent of capacity, and followed a pattern set by the automobile workers and other unions as a result of the economic slump. In another set of negotiations, the United Automobile Workers and the Chrysler Corporation are to return to the bargaining table in an effort to resolve an impasse. (Page D16.)

The sharp decline in the British pound this week has created a mixture of jubilation and concern among businessmen and politicians here. After a three-day plunge, the pound stabilized today in trading against other currencies, and edged higher in trading in Europe and the United States. The decline, which on Wednesday briefly took the pound below the $1.60 mark for the first time in six years, has been comparable to a 3 percent to 4 percent devaluation against most currencies. Its impact, if sustained, would be to improve the competitiveness of British industry at home and abroad by making British goods relatively cheaper.

On Canada's Remembrance Day, Nov. 11, some 70 workers at Stelco Inc.'s sprawling steel mill here pinned on aging combat decorations and marched beneath a metallic sky to bagpipes and drums. Old-timers recalled when upward of 450 war veterans would join the annual observance. The sense of loss was magnified this year. Some 6,500 of Stelco's labor force of 18,000 have been laid off or will be by the end of the year, and most of those remaining face a grim Christmas. More than three-quarters will be placed on unpaid furlough from Dec. 18 to Jan. 2.