What was going on when I was born?

The cost of a ride on the city's subways and buses was raised yesterday to 90 cents, a 15-cent increase. The new fare, to take effect next month, is the first increase in two and a half years. The increase was approved by the board of the Metropolitan Transportation Authority, which also voted higher fares for its rail commuters and raised some bridge and tunnel tolls. Fares will rise an average of 20 percent on the Metro-North Commuter Railroad and the Long Island Rail Road. Bridge and Tunnel Fares Tolls at four bridges and two tunnels operated by the Triborough Bridge and Tunnel Authority will go to $1.50, from $1.25.

A steady 10-year decline in New York City's welfare rolls has ended, and in the last year the number of people on welfare has risen to more than 900,000. A substantial part of the growth in welfare rolls, city officials said, can be traced to a growing number of single people who cannot find employment and must rely on public assistance to live. ''Welfare rolls go up when there is unemployment and broken homes,'' Mayor Koch said. ''Regrettably, both factors exist today as causes for the increase.''

President Raul Alfonsin said today that he had set up a commission to investigate the disappearances of more than 6,000 Argentines during the military Government of the last several years. He said evidence turned up by the panel would be given to the courts for prosecution. It was the latest in a series of forceful measures Mr. Alfonsin has taken in his first week in office to rectify the abuses of nearly eight years of military rule. The nature of the actions and the speed with which the new President has ordered them have surprised many Argentines.

Billy Martin's third term as manager of the Yankees ended with his dismissal yesterday, almost a year after it began. And Yogi Berra's second term began, 19 years after his first one ended. The change was the 11th in 11 years made by George Steinbrenner, the principal owner of the team, who said: ''I don't like to talk about firing managers. I'm shifting people in everyone's interest: Billy's, Yogi's, mine.''

The Producer Price Index, the leading gauge of industrial price changes, declined two- tenths of 1 percent last month, the first drop since spring, the Government reported today. The Labor Department, which compiles the index, attributed the November decline to 1 percent drops in both food and energy prices. The index is for finished goods, products on which manufacturing has been completed. It has risen less than 1 percent for the last 12 months, its smallest increase since 1964 and another reflection of the overall economy's unexpectedly good health.

The applications of hundreds of Polish nationals for political asylum in the United States have been rejected by Federal authorities trying to clear a backlog of applicants. Most of the Polish nationals have claimed an association with the Solidarity union movement and contend they would face persecution if they were sent back to their homeland. The immigration authorities say there are no statistics at the State Department, the Justice Department or the United States Immigration and Naturalization Service on the exact number of rejections. However, applicants in several parts of the country reported a flurry of recent rejections.

President Reagan today came out in favor of tighter controls over imports of textiles, after persistent pressure from the powerful domestic industry. The action was announced late today at the White House after two days of Cabinet discussions, with members split over the issue. Forces led by Commerce Secretary Malcolm Baldrige pressed for the additional protection, while the United States trade representative, Bill Brock, led those who sought to maintain the status quo. The President's decision followed months of intense lobbying by both producers and workers as well as members of Congress representing textile-producing areas. Since the early 1960's the textile bloc has been successful in winning import protection in election years.

A new cease-fire went into effect in Lebanon today. It was announced in Damascus, the Syrian capital, by representatives of the Lebanese Army and Moslem militia forces, who have been fighting with renewed intensity over the last three weeks. The representatives said they hoped the cease-fire would lead to a reconvening of the talks among the warring factions that ended inconclusively on Nov. 4 in Geneva. As the battlefields fell quiet, the Beirut International Airport reopened after a 16-day shutdown ordered because of heavy shelling. In another development, the state- controlled Beirut radio reported tonight that the Lebanese President, Amin Gemayel, on his way back to Lebanon from two days of meetings with British officials, had spent five hours in ''very positive talks'' with Col. Muammar el-Qaddafi, the Libyan leader.

The Spanish Communist Party, which rose to fame as a fighting force in the Civil War and then to legend as an underground resistance in the Franco dictatorship, is facing its most severe crisis since it was legalized in 1977. After years of disputes, splits and purges, the dwindling party is now flirting with an open rupture that is unfolding in public at a national party congress that opened here Wednesday. The dispute pits Santiago Carrillo, the brilliant, acerbic 68-year-old party warhorse who resigned as secretary general a year ago, against his protege and replacement as party leader, Gerard Iglesias, a 38-year-old former miner from Asturias who is as dapper as a movie star. The implications go beyond domestic politics, since the Spanish Communists have been, along with the Italians, the major exponents of Eurocommunism in Western Europe, a doctrine that in theory upholds democratic elections and emphasizes independence from Moscow. Whether that line will be pursued, and how vigorously, may be decided at the congress, which continues through Sunday.

Queen Margrethe II dissolved Parliament today and scheduled elections for Jan. 10 after the Government's proposed budget was rejected by both rightist and leftist opposition parties. The Queen signed a decree at the request of Prime Minister Poul Schluter mandating Denmark's eighth election in 15 years.

Two bombs exploded at a military installation in northern Spain today, wounding three servicemen and causing extensive damage, the authorities said. E.T.A., the Basque guerrilla group, said in a call to a newspaper that it was responsible for the bombs and that four other bombs were at the site. Military sources said a third bomb was discovered under a propane gas tank and defused.

A British national newspaper complied today with a high court order and returned to the Government a leaked copy of a secret memorandum dealing with the handling of public information on the first cruise missile deliveries this fall. The newspaper, The Guardian, submitted to the order, which the paper's editor said had in effect ''shot full of holes'' legislation designed to protect a newspaper's sources. The legislation was approved in 1981. ''This was the first case under Section 10 of the Contempt Act, which was supposed to give journalists increased protection for their sources, and it has been blown utterly apart,'' the editor, Peter Preston, said after the newspaper returned a photocopy of the memorandum, which was written by Defense Secretary Michael Heseltine to Prime Minister Margaret Thatcher.