What was going on when I was born?

Hackensack, N.J., hasn't had a good time of it since the mammoth Bergen County shopping malls drained the lifeblood out of downtown starting in the 1950's. Now, in a hopeful sign of resurgence, groundbreaking should begin this month on the first phase of a major office development; the work had to await relocation of a big sewer line.

Gerard Schwarz never plays the trumpet anymore. He gave up a career as a virtuoso instrumentalist six years ago in order to conduct full time. Now he is music director of the Los Angeles Chamber Symphony and of New York's Y Chamber Symphony, which he founded in 1977, and of the Waterloo Festival Orchestra in New Jersey. He is also preparing for his opera conducting debut in Washington next season, and this summer he has taken on a new assignment - music adviser to New York's Mostly Mozart Festival, which starts tomorrow night at Avery Fisher Hall. A music adviser isn't a music director, as Mr. Schwarz and the festival's director, William C. Lockwood, are quick to assert, and Mostly Mozart's format of orchestral concerts under guest conductors alternating with chamber-music evenings will remain unchanged. Mr. Schwarz's job, a three-year appointment, will require him to take responsibility for the Festival Orchestra's personnel, morale and development, conduct about one-third of its concerts, and offer program ideas to help the festival expand. Short and energetic, Mr. Schwarz uses the word ''wonderful'' a great deal as he speaks fluently about orchestras, becoming a conductor, and the effect that he expects his appointment to have on the Mostly Mozart festival. ''I think what they're looking for in me is someone to continue to help the orchestra to grow, and to find varied and interesting repertory for the public and the critics,'' he says.

HARTFORD ALL the months of planning, speech-making and wooing of delegates will come down over the next two weekends to a few crucial roll-call votes that will shape the course of the statewide election campaigns for both parties for the rest of this year. It is state convention time again in Connecticut. Political conventions have become anachronisms in some states where the parties rely more on primary elections to choose their candidates. But here the convention system remains strong, and it is rare for a candidate for statewide office to be unseated in a primary election after winning the endorsement of a majority of the convention delegates. Amid all the hoopla of bands, banners and bunting, the two state conventions this year should offer some contrasts to each other and to the conventions of four years ago.

Negotiations for a settlement of the Lebanon crisis made little headway today, amid indications that the Palestine Liberation Organization has no intention of withdrawing from Beirut without major political concessions. Israeli armored units in the hills surrounding west Beirut traded intermittent artillery fire with the Palestinian guerrillas trapped inside, after a night of fierce Israeli shelling. Lebanon's Prime Minister, Shafik al-Wazzan, President Elias Sarkis, Foreign Minister Fuad Butros and the American special envoy, Philip C. Habib, met at the presidential palace in Baabda, overlooking Beirut, but there was no reported progress in their efforts to find a solution for the Beirut crisis and the withdrawal of the P.L.O. The negotiations have not only become bogged down, but they have become extremely difficult to follow. The present positions of the key parties, Israel and the P.L.O., seem unbridgeable, and confusion over where the negotiations stand is a result of the unusual manner in which they are carried out.

Israel has given United States intelligence officials documents and other information obtained in Lebanon indicating that mercenaries from India, Pakistan, Bangladesh and various African nations were fighting with the Palestine Liberation Organization. At the same time, the Israelis also gave American officials an account of what they considered the surprisingly large stores of weapons seized by Israeli troops in Lebanon. Among those weapons, the Israelis said, were American M-16 rifles that had been sold to Saudi Arabia. Copies of the documents, most of which were given to President Reagan late last month by Prime Minister Menachem Begin, were made available here by Israeli officials.

The Reagan Administration, in its midyear economic forecast, has a relatively optimistic outlook for growth through next year, Administration economists said today. But the forecast still predicts that unemployment will be over 9 percent at the end of this year and will average just below 8.5 percent in 1983. At the same time, a leveling off of the inflation rate at 6.5 percent this year and next is foreseen by the economists. This outlook, which is close to the forecast the Administration made earlier this year, is more optimistic than the views of many private forecasters, who have been scaling back their hopes for recovery next year as interest rates have remained high. The complete Federal midyear forecast is not expected to be made public for more than a week.

WASHINGTON AMID the bloodshed and confusion of the Lebanon crisis, the Reagan Administration may have happened on a course that, while full of obvious risks, holds out the prospect of some windfalls for American objectives not anticipated when Israel invaded Lebanon more than a month ago. Much depends on the negotiations being conducted in Beirut by the Administration's special envoy, Philip C. Habib. If he proves the skeptics wrong and devises a formula acceptable to Israel, the several Lebanese political factions, the Palestine Liberation Organization and Syria, the United States could find itself with the most promising opportunity for negotiations since the Egyptian-Israeli peace treaty was signed in 1979. If he fails, and the Israelis give up on diplomacy and decide to annihilate the P.L.O. forces in west Beirut, the United States could find itself being blamed for sanctioning the inevitable bloodshed. In the uproar over such military action, Washington could be left without much leverage on future Middle East developments.

WILLIE McGEE, now the National League's leading hitter, said he had t wo chances of winning a job with the Yankees -''slim and none.'' S cott McGregor, now one of the best pitchers in the American League, r emembered that he was depressed when a Yankee trade for an e stablished left-handed pitcher ''killed my chances.'' Tim Lollar, the pitcher who now has the best winning percentage in the National League, said he was ''kind of down'' when the Yankees traded him. ''I guess George doesn't have the confidence in young players,'' Lollar said the other day, referring to George Steinbrenner, the Yankees' principal owner. His San Diego teammate, Chris Welsh, went further.

WESTBURY FOURTEEN months after the installation of a new computer system that was intended to expedite the processing of license plates and automobile registrations, delays and frequent computer failures still plague the state motor vehicle office here, and lines of irritated motorists still stretch out onto the sidewalk in front of the building. The situation has so alarmed the officials who operate the office that they now summon Nassau County policemen to maintain order in the crowd, which is heaviest at the end of the month. The office issues more vehicle registrations than any of the 116 other offices in the state - some 917,000 in 1980, the last year for which complete statistics are available. ''We feel the problems with the computer are really worse than last year,'' said Joan Reilly, the assistant to the director. ''We had expected it to be the answer to all our prayers. Now we fear the day the whole state goes on this system.''

After a five-year negotiating seige, the Brooklyn Arsenal Building has fallen to Herbert and Henry Mandel. The Mandels, pere and fils of a family that has been building in New York for four generations, purchased the former World War II armory in Sunset Park from New York State for $700,000 and plan to convert it into back-office and computer space renting for less than $10 a square foot.

Though the official ''topping-off'' ceremony will not be held until July 26, anyone gazing up at Trump Tower at 56th Street and Fifth Avenue can plainly see that the 68-story, 700-foot structure has reached its full height. By far the tallest concrete building in the world, according to its developer, Donald J. Trump, its superstructure took 90,000 tons of concrete and 4,000 tons of steel reinforcing rods to complete.

Siege or slaughter? Hoping to end the one and avoid the other, President Reagan last week agreed ''in principle'' to send American troops to help gain the withdrawal of Palestinian and Israeli forces from Beirut. France also offered ''in principle'' to contribute troops. Deployment hinged on a settlement among the many parties to the dispute, an extremely difficult feat. Some optimism was generated when Lebanon's Moslem Prime Minister left west Beirut for the first time in a week and met with Washington's special envoy, Philip C.Habib, in the relatively comfortable Christian east. But the mood quickly worsened after resumption of heavy artillery and rocket barrages between Israel and the Palestinians. At least 50 people died as the Israelis scored direct hits on still-occupied tenements and abandoned luxury high-rises along Beirut's embassy row.