What was going on when I was born?

Will a new bus and subway token go into use next year? Definitely. In fact, it may happen twice. The Transit Authority plans to issue a new bull's-eye brass token with a round stainless-steel core about the end of February. The new token, however, is not connected with a possible fare increase. The coin is an ''anti-slug'' token. All subway turnstiles will be rewired to accept only this coin in an effort to combat the annual $2.5 million revenue loss from the use of slugs. The turnstiles are expected to be rewired systemwide by the end of May, according to transit officials.

An investor group that owns 9.4 percent of the troubled Kaiser Aluminum and Chemical Corporation offered last night to buy the rest for a package of cash and securities that it valued at $20 a share, or nearly $800 million. If its offer is not taken seriously, it said, it would ''take our proposal directly to the stockholders'' to remove the directors and install its own slate. It also offered to invite several Kaiser executives to remain, but made clear that its aim was to sell off some assets and cut $1 billion off Kaiser's $1.3 billion in long-term debts in ''the next several years.'' Tulsa Investor Heads Group Joseph A. Frates, of Tulsa, Okla., is head of the investor group. Mr. Frates, a prominent Oklahoma investor involved in earlier bids for Revlon and Frontier Airlines, headed a group that bought the Kaiser Steel Corporation, which is not affiliated with Kaiser Aluminum, in 1983, and resold it this year after major restructuring.

The Reagan Administration said today that it would start again to review all 2.6 million people on the Social Security disability rolls to determine if they were entitled to continue receiving benefits. Margaret M. Heckler, the departing Secretary of Health and Human Services, who halted the reviews in April 1984, said today that they would resume next month. Federal judges, governors and members of Congress from both political parties harshly criticized the earlier reviews, charging that thousands of people eligible for benefits had been improperly removed from the rolls. Rules Are Issued Since then Congress has unanimously passed legislation overhauling the disability program. Today the Social Security Administration issued rules to interpret and carry out the 1984 law.

In a session of wild price swings and frantic trading, the blue-chip-based Dow Jones industrial average made history yesterday by briefly piercing the 1,500 level before falling back abruptly. But many secondary shares moved higher, and, over all, more Big Board stocks rose than fell. When the dust settled, 181 million shares had changed hands in the fourth-busiest session ever. But stock prices ended the day mixed, when blue-chip and transporation issues did an about-face late in the day.

Freshly armed with nationally known legal talent, Texaco Inc. pleaded for its life today before a Texas state judge who must decide whether to uphold a $10.53 billion jury award against the company. Gibson Gayle, a lawyer with Fulbright & Jaworski, a Houston law firm, said on behalf of Texaco that that the judgment would ''threaten the very existence of a major United States corporation.'' He characterized the company's prospect of posting a $12 billion bond as ''an enormous economic threat'' hanging over Texaco, its 55,000 employees and more than 300,000 shareholders. But Joseph D. Jamail, the lead lawyer for the Pennzoil Company, which brought the suit accusing Texaco of wresting Getty Oil from its grasp, said that Texaco, by asking for a drastic reduction in the potential damages, was essentially saying that ''if you steal big enough or get hurt big enough, corporate America, don't worry; you won't have to pay.''

Wall Street is wondering what the J.M.B. Realty Company is up to. The big Chicago-based real estate syndicator said yesterday that it had spent about $100 million to gain control of 13.5 percent of the stock of Viacom International, the diversified media company, but at the same time it said it would not attempt to take control of the company. ''J.M.B. bought a lot of that stock at a high price,'' said one arbitrager, who asked not to be identified, ''and now it's not clear how they will get their money back if the company isn't sold. Why buy the stock if you are not going to take over the company?''

The Advertising Column yesterday incorrectly identified the company marketing DeKuyper Cordials. It is the National Distillers and Chemical Corporation.

The State Department's top Latin America official said today that Cuban military advisers had become increasingly involved in combat operations against rebel forces in Nicaragua. Testifying before a House Foreign Affairs subcommittee, Elliott Abrams, Assistant Secretary of State for Inter-American Affairs, said, ''You now have Cubans fighting, not just in Africa, but on the mainland of North America.'' He confirmed a report that the largest Nicaraguan rebel group, the Nicaraguan Democratic Force, shot down a Soviet-built MI-8 helicopter on Monday and that two Cubans were among the 14 casualties. Mr. Abrams said there were about 2,500 Cuban military advisers in Nicaragua, ''and they aren't just advisers.''

An article in The Home Section yesterday on women and housework misstated a finding by Joann Vanek. She found that women without jobs outside the home spend more than 50 hours a week on housework; the others spend half that.

Opposition leaders said today that they had agreed to unite behind a single candidate to oppose President Ferdinand E. Marcos in elections scheduled for next year, and they indicated that the nominee would be Corazon C. Aquino, the widow of the assassinated opposition leader Benigno S. Aquino Jr. The opposition figures made it clear that Salvador H. Laurel, a former senator who had been the first opposition leader to announce his candidacy for President, had accepted the offer of the vice presidential spot on a ticket headed by Mrs. Aquino. Mr. Laurel told reporters today that the two candidates, who have been meeting privately to seek a unified slate, would hold a joint news conference on Sunday. He said the news conference would announce ''the official candidate of the united opposition.''

Markets The Dow Jones industrial average briefly sailed past 1,500 in a session of frantic trading, but then fell back abruptly to close the day with a loss of 1.49 points, at 1,482.91. Many secondary shares moved higher, however, and over all, more Big Board stocks rose than fell. About 181 million shares were traded in the fourth-busiest session ever. [Page D1.] The burst of investor enthusiasm that has pushed the Dow up nearly 200 points since late September stems from a decline in interest rates and the fear among pension fund money managers of missing a rally. It also reflects growing hopes for a narrowing of the nation's trade and budget deficits. [A1.] The credit market showed modest losses as traders anticipated the large rise in the money supply that was announced late in the day. The $4.4 billion increase for the week was partly attributable to technical factors. But economists say there are a number of signs that the lull in rapid money growth has ended. [D1.]

ONCE again it's time to head for the country to pick and cut your own Christmas tree instead of going down the street to the nearest store that sells trees already cut. Within an hour or two of Times Square, scores of Christmas tree plantations have opened for the season, offering growing Scotch pines, Douglas firs, white pines, blue spruces and other varieties for those venturesome enough to seek them out in their native habitat. There are few better ways for families, especially those with children, to get into the Christmas spirit than by an expedition to a rural area where the trees are growing on commercial plantations that are geared for choose-and-cut sales. But before you go, telephone to find out directions, if the farm still has a supply of trees and whether it is open for cutting. Last week, for example, several farms in upstate New York were closed because ice had formed on the branches of the trees.