What was going on when I was born?

Citicorp, the nation's biggest banking organization and one of the largest employers in New York City, announced yesterday that it had taken steps to establish a bank in Delaware where the tax rate averages 3 percent compared with a 26 percent rate for big New York banks. It is expected that much of the future growth in Citicorp's banking business would be channeled through the proposed Delaware subsidiary. Currently, Citicorp employs 17,000 people in the New York metropolitan area. Although it is not expected that the establishment of a subsidiary in Delaware would reduce this number, analysts contend that it could seriously reduce any growth in Citicorp jobs in the New York region.

Du Pont exercised an option yesterday to purchase 15.9 million new shares of Conoco stock directly from the oil company for $1.4 billion, and Conoco's chairman turned aside rumors that Conoco's big coal subsidiary would be sold off after the merger with Du Pont. The idea is ''utter nonsense,'' said Ralph E. Bailey, the chairman of Conoco, at a press conference. ''The coal company is a very important part of the new Du Pont, and it will not be sold.'' Many analysts had predicted that Joseph E. Seagram & Sons might ask Du Pont to exchange all or part of Conoco's Consolidation Coal Company, the nation's second-largest coal producer, for Seagram's interest in the combined company, expected to be about 18 percent.

Texas International Airlines won a round today in its fight to take over Continental Air Lines, as the Civil Aeronautics Board instructed its staff to draw up an order approving the proposed acquisition. The action dealt a blow to Continental's efforts to thwart Texas International by selling newly issued shares to an employees' association, through an Employees Stock Option Plan that would then assume control of the airline, but spokesmen for Continental and the employees association said that the effort was not dead. ''We'll never quit,'' said Chuck Cheeld, a Continental pilot and adviser to the employees' association . ''We'll fight this thing to the very end,''

Officials at the Federal Aviation Administration's training academy said here today that they expected the first candidates in their new, more ambitious program for civilian air traffic controllers to be selected shortly from a Civil Service eligibility list of 7,500 people and to be sent here this month. They are prepared, the officials said, not only to expand training operations from the current eight-hour-a-day training schedule to a three-shift, 24-hour-a-day schedule within 30 to 60 days, tripling the nation's output of new controllers, but also to accelerate work on a variety of innovative techniques to further speed the availability of qualified new controllers. ''We're ready to get up and go the minute we get the word to increase the training here,'' said Edwin Harris, the superintendent of the academy, a complex of low-slung buildings that looks much like a college campus sitting amid the Oklahoma plains. ''We have the capability, the training space and instructors to start at any time.''

''From Vines to Wines'' is the new photography exhibition opening today at the French Institute, 22 East 60th Street. The 51 black-andwhite and color pictures on view are the work of Peter Aaron, film maker and photographer. Mr. Aaron took his camera to the Bordeaux wine-growing region of France, where he photographed ''vignerons'' in the cellars of some of the most famous chateaus - Latour, Haut-Brion, Mouton-Rothschild. ''From Vines to Wines'' will be on display through Sept. 25. No admission charge. Hours: 10 A.M. to 6 P.M. Monday through Friday. Information: 355-6100. PHILHARMONIC ROLLS ON The New York Philharmonic is on the move this weekend with its free concerts. Tonight at 8, the orchestra will be at Cunningham Park in Queens. And Sunday night at 8, it will be in Westchester for the first time in the 17-year-old outdoor series, appearing at the Westchester Community College football field in Valhalla. Both concerts will be conducted by Lawrence Foster, music director of the Philharmonic Orchestra of Monte Carlo, and both will offer music by Wagner, Kodaly and Dvorak. Information: 877-5224.

The Reagan Administration, dispatching dismissal notices to more of the 12,000 striking air traffic controllers, turned its emphasis today to ''rebuilding the system'' with accelerated training of recruits and better use of those available to work. ''As far as I'm concerned,'' Transportation Secretary Drew Lewis said at a news conference late this afternoon, ''it's a nonstrike situation. It's over. Our concern is rebuilding the system.''

In scorn, they called it ''Clinton's Ditch'' when New York's Governor De Witt Clinton decided to construct it in the early 19th century. But the Erie Canal paid for itself within eight years of its completion, and state officials now hope to keep it productive by harnessing its water power to produce electricity. During a leisurely trip up the canal today, officials of the State Energy Office showed off their small hydro-projects and preached the gospel of alternative energy sources. In the process, they also showed that what is out of style in one era can become quite fashionable in the next. ''There's a generation in there where people did not get hydropower engineering,'' said Parker D. Mathusa, an official of the state's Energy Research and Development Authority, referring to the training given the nation's power experts. ''It was a passe art, like blacksmithing.''

YORK By GRACE GLUECK OVER the city they spread, gradually infiltrating the parks, the plazas, the malls, the bridges, the campuses, the shorelines - even the trees and the walls of buildings. They are New York City's outdoor sculptures, a rich proliferation born of an interaction between the city's thousands of artists and its astoundingly varied sites, from the beach at Battery Park City to wooded parks in the Bronx. Hardships don't faze the makers of these outdoor attractions: finding sponsors, locating sites and getting the works to them is all part of the game. And more often than not, the city is the better for their contribution. For a weekend sculpture safari all the equipment that's needed is a a pair of comfortable shoes and maybe a picnic lunch. And here, starting at the top (in the Bronx), is one way to carry it out. Wave Hill, the city-owned nature center in the Riverdale section of the Bronx, is a captivating site on the bank of the Hudson with rolling lawns, civilized woods and genteel gardens - in short, a foolproof setting for outdoor sculpture. Each summer since 1977, the curatorial team of Linda Macklowe and Suzanne Randolph has made the most of it, with a themed show deployed around the grounds. This year they offer ''Tableaux,'' on-site works by nine invited artists, who - with varying degrees of success - have carried out the notion of a ''frozen'' scene or action.

Treasury Secretary Donald T. Regan said today that the Federal Reserve Board would have to ease up on monetary restraint to avoid a severe recession. Mr. Regan, in an interview, expressed concern that the continued slow and below-target growth of M-1B, a key measure of the nation's money supply, could push the nation into recession from the current period of economic slowdown. ''What I am suggesting,'' said Mr. Regan, pointing to a chart of the recent growth of M-1B, ''is that, if it stays here, you're going to have a severe recession. You've got to come into the low end of the range.''

The Soviet Union has recently rebuffed several efforts by the Reagan Administation to start secret discussions on a possible political settlement of the fighting in Afghanistan, according to State Department officials. Messages passed to Soviet diplomats in Moscow and Washington in the last two months, the officials said, were intended to convey an understanding of the Russian concerns in Afghanistan, a willingness to discuss internal political compromises there and a sense of the importance of the Afghan issue to future Soviet-American relations. The officials said that the United States policy since the largescale Soviet military intervention in December 1979 had remained the same - to get Soviet troops out of Afghanistan. The officials described what amounted to a shift in strategy: to convince Moscow that it could not win against insurgent guerrilla bands in Afghanistan and that it should therefore take up the American offer to provide a face-saving diplomatic exit that would take Soviet interests into account.

Controllers' Strike The dismissal of all controllers taking part in the illegal four-day strike was proceeding as the Reagan Administration shifted its emphasis to training new recruits and ''rebuilding the system'' with a virtually entire new staff. The Administration said that the 12,000 strikers who had defied an ultimatum to return to work or forfeit their jobs would soon be off the payroll, except for a few with valid excuses. The Government also reported that air traffic continued to rise, reaching 79 percent of the 14,200 normal daily flights. (Page A1, Column 6.) Preparations to train new controllers were being made at the Government's academy in Oklahoma City. Officials said they were prepared to triple the nation's output of flight controllers to 5,500 or more a year. (A1:5.)

The current takeover favorite is Cities Service. Its shares surged 2 1/2 points on the New York Stock Exchange yesterday. But the Marathon Oil Company, with that big West Texas oil field, looks awfully enticing. And how about Union Oil of California, which is swollen with natural gas? It's probably too big to swallow, but who knows? After Conoco, anything is possible. Du Pont's $7.57 billion takeover of Conoco Inc., the nation's ninth-largest oil company, has prompted speculation that other large oil companies might also be takeover targets. Almost everyone on Wall Street, it seems, is guessing what will be next, and stock prices are rising on the speculation, which encompasses Kerr-McGee, Superior Oil, Pennzoil, Getty and Louisiana Land and Exploration? ''It has been the biggest game in town,'' said Robert C. LeVine, an analyst at E.F. Hutton. ''It's been the only game in town. We didn't even have baseball this summer, so we used this as the national pastime.''