What was going on when I was born?

THE lack of affordable housing on Long Island for moderate-income families has prompted officials in towns in both Nassau and Suffolk Counties to re-evaluate their local zoning and housing codes. At issue in many localities is the creation of special zones for apartment houses as well as the legalization of the now-widespread but prohibited practice of two families sharing a house designed for single-family occupancy. The scarcity of mortgage money as well as high interest rates on available mortgages has forced more middle-income families out of the buyers' market and into the rental market in recent years, making the existing housing shortage more acute, according to Dr. Lee Koppelman of the Nassau-Suffolk Regional Planning Board. Statistics provided by the Regional Planning Board place the average income of a Long Island household at $22,000. Mortgage rates from Long Island banks are now placed at 17 3/4 percent up to 19 percent plus points.

Not long ago a top adviser to President Reagan was outlining the gloomy situation the Administration faced in bolstering the Government of El Salvador. The picture included diminishing chances of a fair election March 28, increasing prospects of a military stalemate with the Salvador insurgents, and growing skepticism about the wisdom of Mr. Reagan's course. Asked what the Administration was doing in light of its pessimistic assessment, the adviser threw up his hands. ''We're reviewing the situation,'' he sighed. ''What does the Government always do? We're reviewing it. What would you do?'' The tone of exasperation seems pervasive these days. A year ago, White House officials recall sourly, Secretary of State Alexander M. Haig Jr. was assuring Mr. Reagan that the war in El Salvador could be ''won'' with some additional American aid. Today the President is being advised that the United States faces a ''long haul'' there - perhaps five or six years. Whether Congress, the people or America's allies can accept a longterm commitment to El Salvador remains an open question, particularly in light of the sputtering attempts last week to launch an information campaign about the threat perceived in Central America. It is also unclear whether the public is prepared to support covert activities there by the Central Intelligence Agency, which was said to have been planning the financing, organizing and supplying of arms for paramilitary operations aimed at disrupting Cuban arms deliveries to El Salvador and elsewhere.

THE fate of the $135 million Hempstead Resource Recovery plant, which has been idle for the last two years, may be decided in the next few months despite the continuing debate about its viability as a solution to Hempstead Town's garbage-disposal problem. Several recent developments involving the plant -where incineration was halted in March 1980 during a contract dispute that pitted town officials against the plant's private owner and operator, Parsons & Whittemore Inc, - have suggested that a framework is emerging in which some issues can be resolved and the facility put back in operation. These include the following: - The consensus of the town advisory comittee on solid waste disposal that the plant should be reopened for another round of emissions tests. It arrived at this conclusion after it was unable to find any alternative methods of dealing with the town's garbage problems.

Often overshadowed by fundamentalism and shunned by church liberals, the mainstream of evangelical Christians has emerged as the most powerful new force in American Protestantism. These evangelicals, mostly moderate in theology and politics, have been growing in numbers for years. But now they are strengthening their own institutions and making deep inroads in the 50-year-old liberal leadership of the major Protestant denominations. The signs of evangelical vitality are seen in the robustness of student movements, in the enthusiasm of lay people and in the clergy, which is well-equipped by education and outlook to bring the historic tenets of the Protestant faith to bear on 20th-century problems. Another sign is a recent decision by the Harvard Divinity School, a pillar of Protestant liberalism, to establish a chair in evangelical studies. Other old-line seminaries are expanding in similar ways. The influence of leading evangelical publications has expanded and a large network of professional, educational and lay groups amplifies the evangelical voice.

TRENTON GOVERNOR KEAN will not formally present his first budget message to the Legislature until tomorrow. However, key elements of the $6.37 billion document were released by his top aides in two briefings last week, and Democrats in both the Senate and Assembly are already howling that homeowners will be gouged on their property taxes so that business taxes can be cut. Objections voiced by the Democrats showed little of the bipartisanship spirit that Mr. Kean appealed for in his inaugural address in January. Their complaints about some of the budget's key philosophical underpinnings -cutting state aid to municipalities to help offset reductions in business taxes and a big $729.4 million deficit -were so intense that the Governor's aides retorted that the budget was ''not written in stone.'' They invited the Democrats to offer alternative plans, but none was immediately forthcoming. After all, the entire budget was not released from the printer until Friday night, and none of the Democrats controlling both houses of the Legislature has studied it in detail.

OPEC's Last Waltz? Times have never been worse for OPEC. Oil prices keep slipping, economists keep pushing back estimates of the strength and timing of recovery in major consuming nations, and the cartel's own revenues are falling sharply. So the OPEC gathering in Vienna this week is likely to be a critical and cantankerous one. Much of action may take place before Friday, when the session formally begins, says Philip Verleger, an oil analyst with Booz Allen Hamilton. In order to defuse bickering about future production levels, Saudi Arabia, which has cut ouput by roughly 3 million barrels a day in the last 12 months, to 7.5 million, may announce more cuts as well as a price drop of around $2 a barrel. However, those steps may not be enough, Mr. Verleger says.

A dozen years ago, in an America of cheap energy and 7 percent mortgages, California-style house, with their steeply pitched rooflines, glass walls, oversized windows, wooden siding and earth-tone colors, were the rage in model homes throughout the East. Decorated in blues, reds, and yellows, plastered with mirrors that made their open designs seem even more spacious and scented by sprigs of imported aromatic eucalyptus, the California models were promoted as the shelter of the future: Down with the restrictive Eastern colonial boxes, proclaimed the ads, up with openness and freedom. In 1971, the Larwin Group, a Los Angelesbased builder, opened Greenbrook, a development of California houses in Coram, L.I., where the asbestos-shingled, L-shape ranch and the two-story center-hall colonial of Levitt and Sons dominated. Levitt already had started building California homes in Strathmore East in Coram. Kaufman & Broad, another national builder, had also opened a development in Coram, selling colonial as well as California homes.

HOW to describe the underlying condition of the American economy? Short-term, it is obviously in a recession that started last fall; but this is the second recession since 1980, the third since 1975, and many economists believe that, even if recovery begins in the second half of this year, a fourth recession is just around the corner. It's been a long sequence of recessions and weak, aborted expansions. Is this, then, a depression we are in? Looking backward, the term seems too strong. The economy has been stagnating, not collapsing. If the roof were to fall in later this year, or next, it could become a depression, but the odds are still against it. Call it repression - a chronic state of underemployment and industrial slack that has dogged the economy for the greater part of the past decade, a condition brought on by repressive actions of governments in the industrial world to cope with inflation, energy shortages and currency disorders.

The Reagan Administration is abandoning major components of its plan to hold down medical costs by spurring competition, according to Administration and Congressional sources. The plan has been opposed by major businesses, organized labor, the insurance industry and medical groups. Almost certain to be dropped is a widely discussed proposal to place a limit on the amount of employee health benefits that private employers can deduct from their taxable income, with any additional benefits treated as ordinary taxable income. The plan, which was meant to reverse the existing tax incentive to offer richer and richer benefit plans, was resisted by both big business and labor, as well as by some Government agencies.

Developers trying to compete in the lucrative luxury condominium apartment market here are building apartments with finishes and amenities that are probably the most sumptuous offered on a large scale anywhere in the United States. Everybody seems to be building marble bathrooms. Dade County may have more bidets per capita than any county in the country. So-called ''Roman tubs,'' many with whirlpool features, are standard in a market where apartments range from $125 to $200 a square foot. The apartments are typically 1,500 square feet, though they run from 1,300 to 3,000. ''It's a battle,'' said Lewis Goodkin, a market research specialist who advises developers on amenity programs. ''First it was the big tub. Then it was the big tub with the separate shower. Then it was the bidet, even though some people think it is a drinking fountain. All it takes is one developer who outsells the market place.''

SOMERS THIS rural town of 13,000 in the hills of northern Westchester is preparing for a new role as host to a big company of the kind that made ''campus'' office parks a notable feature of the ''Platinum Mile'' from Tarrytown to Rye. No commercial development of the magnitude suggested by Pepsico Inc. has ever been built in Somers. Heritage Village, a 6,000-resident development, was begun in the 1970's and, although not completed, has ''basically doubled the assessed valuation and population'' of the town, according to Richard R. Oehler, Chairman of the Planning Board. More changes to the landscape and density are in store for the town, however, if Pepsico can gain certain zoning and easement concessions before April 10. The conglomerate, with headquarters in Purchase, has proposed building an office complex of 400,000 square feet of floor area on a 211-acre site it has purchased subject to securing zoning changes.

A senior Administration official said today that the problem in El Salvador was global in nature and that the United States should involve the Soviet Union, Cuba and other Latin American nations in the search for a solution. ''We have to talk to the Russians,'' the official said. ''There are discussions that must be held, there are steps that must be taken in political, economic and security areas which tend to influence calculi in Moscow, in Havana, in Nicaragua and in the regional context, and it is a very complex mosaic of interrelated actions which must be consistent, credible and hopefully will ultimately bring a successful outcome.'' There have been inconclusive United States discussions on El Salvador with Soviet, Cuban and Nicaraguan officials. In recent weeks President Jose Lopez Portillo of Mexico has urged the United States to become more actively engaged in contacts with the Cubans and Nicaraguans.