What was going on when I was born?

Mayor Koch yesterday established new guidelines aimed at reducing the diversion of emergency ambulances that carry heart attack victims to hospital emergency rooms and coronary-care units in New York City. Hospitals have refused to accept some ambulances because of overcrowding.The guidelines establish strict conditions for diversions and time limits on any delay in care resulting from them. The Mayor said the new guidelines were ''a responsible beginning for our continuing efforts to safeguard the effectiveness of the city's 911 emergency medical system.''

AUDREY HOCHBERG's decision to seek election to the State Assembly from a newly formed 86th District, which includes Scarsdale, where she lives, as well as White Plains and three-quarters of New Rochelle, apparently has cleared the Democratic field - except for Paul Feiner, also of Scarsdale, who made his bid official last week, too. Mr. Feiner, a 26-year-old lawyer and political gadfly, would seem to have little chance to succeed against Mrs. Hochberg, a six-term County Legislator, but politicians and others have learned not to scoff at the activist's efforts, no matter how long the odds. In this primary race, the odds against him are long, indeed. He is challenging an established and well-liked Legislator who has won reelection by wide margins. With Democratic district leaders lined up against him, he will have to seek nomination through the costly and time consuming petition process, rather than through designation.

LONDON PRIMARY principles of modern war on which vast modern military establishments are based are under test in the battle raging on, above and around the Falkland Islands. The outcome of this small, savage war between Britain and Argentina can answer some of the rude questions that trouble the mystique of sea power and perhaps much more. The Royal Navy has exercised its power traditionally, projecting strength 8,000 miles from home bases to enforce a blockade and support an invasion. The operation differs little in concept, but much in strength, from the amphibious campaigns waged by Adm. Chester Nimitz and Gen. Douglas MacArthur four decades ago in the Pacific. The essential difference lies in the introduction of radar-controlled missiles and torpedoes. These Exocets, Stingrays, Rolands and Rapiers are the highly sophisticated descendants of the ''smart bombs'' first used in Vietnam and the second generation of missiles employed in the Arab-Israeli war of 1973.

LIDO BEACH AMONG other unmistakable signs announcing the beach season's arrival has been the continuing escalation of a controversy between Nassau County and cabana renters at Nassau Beach over the status of 498 deteriorated cabanas here. For over seven years cabana renters, seeking to have the 35-year-old units upgraded, have been engaged in on-and-off litigation with the county to determine whether the units should be rehabilitated or destroyed. The issue boiled over again last week when the County Board of Supervisors voted unanimously to spend about $277,000 in general funds to repair the units and improve the grounds, over the objections of Francis T. Purcell, the County Executive, who wants the cabanas torn down. Mr. Purcell vowed to veto the measure within the week. The veto would be the first invoked by the Nassau County Executive in his five years in office. Mr. Purcell said he expected the veto to be overridden.

NEW LONDON CONNECTICUT COLLEGE has begun the largest fund-raising effort in its history and the most significant change in academic direction - and marketing strategy - since admitting men 13 years ago. Administrators, alumni and many faculty members see the four-year, $30 million Campaign for Connecticut College as the greening - in terms of diversity and dollars -of the 1,600-student liberal arts college on the banks of the Thames River. But to a persistent, if apparently smaller, number of student and faculty critics, the campaign is a sell-out. Although they support the initatives for increasing financial aid for students and salaries for the faculty, they contend that the program recommended by the Committee of Connecticut's Future would shortchange the humanities to strengthen mathematics, sciences and athletics. ''I really see the campaign as the responsibility of the college in the 1980's,'' said Oakes Ames, the president of the college since 1974. ''If we are successful - and I trust we will be - Connecticut College will be even more attractive than it is today.''

Starting Thursday and continuing through Sept. 13, Grand Central Terminal - the landmark Beaux Arts railroad station that barely escaped the wrecker's ball some years back - will be on view in two places in Manhattan. The monumental terminal itself, of course, remains where it has always been since its completion in 1913, on 42d Street straddling Park Avenue.

THE house has grown too small. Maybe you just want to move up to a f iner house. Perhaps the kids are growing and, for the sake of h armony, everybody in the family needs more privacy. Husbands and w ives may want separate study areas. Or there may have been job p romotions and raises and you figure you ought to be able to live b etter. In the old days, the answer was simple: You just traded up to a bigger or better house. But a quick tour of the houses on today's market and a few phone calls to bankers about financing have a way of drowning such plans. If you bought your house for $60,000 a few years ago, when interest rates were only 8 percent, your monthly payments are only $440. The same mortgage at 18 percent today would cost you $904 a month and you would not have a better home. To meet changing family needs, those with money are usually improving, remodeling, and expanding their existing homes. Is it a good idea for you? It depends upon your neighborhood, the current value of your home compared to the rest of the community, the size of your lot, the kinds of improvements you want to make, the amount of disruption and aggravation you can tolerate and how long you plan to live in the house if you do make the improvements.

''The fastest-growing industry in the United States,'' a Government official joked recently, ''is public art.'' The statement isn't so far-fetched. Public art blossomed in the 19th century, with its rage for battle monuments and statues of heroes on horseback. Another surge came in the 1930's and 40's, when - as Depression aid - the Treasury Department and the Works Progress Administration gave to hundreds of artists commissions for public buildings. But there has probably never been such a proliferation of art for public sites as in the last two decades. Spurred by grants from the Federal Government, local ordinances that give a percentage of public building costs to art, commissions from image-building corporations, and the belief by business and civic leaders that art will enhance the ''quality of life'' in their communities, an invasion of monumental proportions has spread throughout the country. And in many areas, including New York, it is causing intense debate. Selected for the most part by art professionals, but not always loved by those who have to live with them, the new public icons adorn buildings, plazas, parks, malls, meadows, subway stations, electronic billboards -even rivers and city dumps. Their raison d'etre is the notion that art benefits the community, but unlike the old-style commemorative works, they tend to be abstract, and to celebrate the creative process of a particular artist, rather than a person or event.

HARTFORD'S stately Wadsworth Atheneum, the oldest art museum in the country, is not above airing its dirty linen in public when it can draw a paying audience and help keep the budget in balance. The cost of washing six 18th-century tapestries to be exhibited next year was estimated at more than $13,000, a sum that dampened the spirits of the institution's directors. But by creating a public event out of it and collecting contributions from spellbound laundry buffs and art lovers, at least some of the expenses will be defrayed.

THE Minnesota Twins are the youngest, the least experienced, and the most poorly paid team in baseball. It may not come as a shock to learn that they also have the worst record in baseball - 12-30 - and hold last place in the American League West. The Twins, who complete a weekend series with the Yankees today at the Stadium, have 13 rookies on their 26-man team (one player is on the disabled list); most teams carry perhaps two or three rookies. The Twins have started as many as seven rookies at one time. They have also been involved in several trades this spring that resulted in the departure of their more experienced players. The average age is 25 1/2, and several of the players have only recently come out of the lowest levels of the minor leagues. The average age for the rest of the American League is 28.

A rare public appearance by Leonid I. Brezhnev last week was a clear sign of the political importance the Soviet leadership ascribes to nuclear arms control. For 30 minutes, the obviously feeble Soviet leader stood and addressed a Kremlin audience, expressing approval of President Reagan's offer of new strategic arms negotiations but attacking his proposals for deep cuts in missile warheads as aimed at achieving superiority for the United States. Mr. Brezhnev had a proposal of his own - for a mutual freeze on the numbers and modernization of nuclear weapons once talks begin. The Reagan Administration promptly rejected that idea, as it has similar freeze suggestions, saying it would ''only codify existing Soviet advantages.'' But officials greeted the Brezhnev speech as generally positive. Secretary of State Alexander M. Haig Jr. told reporters in Luxembourg, where allied foreign ministers endorsed Mr. Reagan's plan, that the United States had formally offered to begin talks at the end of June.

HAUPPAUGE SUFFOLK COUNTY is signing contracts to purchase development rights to 3,354 more acres of farmland in a second phase of the Farmlands Preservation Program. Lee E. Koppelman, director of the County Planning Department, said he expected to complete negotiations with farmers and other landowners next month. The purchases will be added to development rights to 3,200 East End acres bought in the program's first phase. Phase-two purchases approved by the county's Farmlands Select Committee include 397 acres in Brookhaven, 30 in East Hampton, 131 in Huntington, 916 in Riverhead, 749 in Southampton and 1,129 in Southold. The total cost is $9.6 million.