What was going on when I was born?

The Postal Service agreed today to pay a total of $400 million in back pay due employees because of violations of the Fair Labor Standards Act from 1974 to 1978. The 800,000 current and past employees affected will get a maximum of $736 each. The pay is due for such things as overtime, night differential, and holiday work. The award, the largest of its kind, was approved today by Chief Judge Aubrey E. Robinson of the United States District Court for the District of Columbia to settle several lawsuits, including a complaint filed against the Postal Service in 1978 by the United States Labor Department.

Gabriel Garcia Marquez, the author of ''One Hundred Years of Solitude,'' was awarded the 1982 Nobel Prize for Literature today. Comparing him to Balzac and Faulkner, the selection committee of the Swedish Academy described Mr. Garcia Marquez, a 54-year-old Colombian who lives in Mexico, as a great novelist of overwhelming narrative talent, breadth and epic richness. More unusual was the academy's defense of its choice with an elliptical reference to laureates of past years whom some people have found inaccessible, esoteric or even unread. 'International Successes' Noted Pointing to the sales in the millions of copies of Mr. Garcia Marquez's best-known novel, the academy asserted it could not be said this time to have given the award to ''an unknown writer.'' ''His international successes have continued,'' since the publication of ''One Hundred Years of Solitude,'' the academy's statement went on. ''Each new work of his is received by expectant critics and readers as an event of world importance, is translated into many languages and published as quickly as possible in large editions. Nor can it be said that an unknown literary continent or province is being brought to light with the prize.''

NEVER let it be said that New Yorkers do not love their city, despite the exuberant grumbling that identifies the species. Every weekend they pour into the streets of the five boroughs, ready to lay their skepticism aside and admire - and learn about - New York. Some explore haphazardly, opening themselves to the random sights and sounds and smells of the city. Others are more orderly about it, winding methodically through a neighborhood, guidebook and camera in hand. But most rely on the walking tours that have grown into a major weekend industry over the last 10 years or so, tours that explore historic or natural areas, that trace the footsteps of some noted New Yorker or simply offer a look in depth at a familiar landmark. Tours this weekend will take gregarious walkers from the promenade in Brooklyn Heights to the quiet paths of Woodlawn Cemetery in the Bronx, in the clear, bright air of autumn. Looks at the legends of Wall Street will be offered, as well as of the people who are celebrated as legends in the statues and monuments of Riverside Park. For those who savor the outdoors in undiluted glory, there will be a windy stroll across the George Washington Bridge and a walk through a salt marsh in Brooklyn.

''We believe the time has come to stop talking about talking about peace and start sitting down at the table, negotiating directly between Israelis, and Arabs, and the United States, and start achieving Palestinian rights, and start achieving the broader peace which is the key to the stability and security for Israel.'' - Excerpt from a State Department policy statement. (A1:6.)

WHAT is the perfect way to watch the New York Marathon? To run in it, surely - a privilege that will be denied all but 16,000 of the more than two million people who will turn out on Sunday to be part of it. The lucky entrants will see some authentic New York curiosities: Fort Wadsworth at dawn, for one, the Staten Island gathering point for runners on their day of days. Think of it: a tiny middle-American town just like John Glenn's, all tended lawns and flagpoles, surrounded by scrub forest aglow with October russets and golds. Incongruous, to be launched from that peaceable kingdom into the chaos of a race where a runner bashes around the corners of the city like a pinball, deafened and buoyed by the din of humanity. Oh, sure, you can watch the Marathon on television. Last year, according to the ratings, 11.5 million people did. This time, ABC has rounded up a few of the usual suspects (Jim McKay, Marty Liquori and Diana Nyad) at honcho central to broadcast three hours of coverage starting at 10:30 A.M. They've got 25 cameras and two helicopters, and runners all over the country are proud that their sport will be getting such major-league attention. There is just one problem, though. The cameras are going to miss the most extraordinary aspect of the Marathon - the part that is truly worth seeing.

In hourly radio reports, nightly news broadcasts and column after column of tiny, gray statistics, the stock market news has been flooding the nation: record volume of shares traded, near-record spurts in the stock market averages. The numbers dwarf anything that has come before. At least on paper, the value of the issues traded in the market has risen some $350 billion in barely three months, as the widely watched Dow Jones industrial average climbed from less than 780 in early August, to 1,036.98 yesterday, spurred by rapidly falling interest rates. If the market's gain of more than 30 percent in just 10 weeks were not impressive enough, President Reagan has hailed the market as the harbinger of the long-awaited economic recovery. But some analysts, including many business executives, caution against attaching too much weight to the market's performance, or to its significance to most Americans.

W. Averell Harriman announced yesterday that he and his family had given $11.5 million to the Russian Institute at Columbia University to promote American studies of the Soviet Union, which many experts fear have fallen to dangerous levels. Standing in front of Chinese vases from the Shang and Chou dynasties at Low Memorial Library, Mr. Harriman, who was Ambassador to the Soviet Union from 1943 to 1946 and Governor of New York from 1955 to 1959, said that American ignorance of the Soviet Union was ''very dangerous'' and that a revival of Soviet studies was ''very important, not only for the academic world but also for the security of our nation.'' ''It is absolutely essential that this country know what is going on in the Soviet Union,'' Mr. Harriman said.

The West German central bank lowered its bank lending rates today in an effort to help revive Europe's stubbornly stagnant economy. Central banks in Austria, the Netherlands and Belgium quickly followed suit. West Germany's Bundesbank announced the most dramatic cuts, lowering its rates by one point. The new discount rate is 6 percent, its lowest level since February 1980, and the Lombard rate 7 percent. These rates are charged commercial banks when they refinance loans at the central bank; the discount rate covers loans for which there is cash collateral, while the Lombard is for loans where securities are collateral.

The United States has proposed to Japan and Western European nations that they agree, as one step toward ending the dispute over pipeline sanctions, not to sign any additional contracts to import Soviet natural gas. Reporters here were told of continuing efforts to resolve the dispute on condition that the source not be identified. If an accord can be reached, the Reagan Administration is expected to lift the trade sanctions it has imposed on European companies that use American technology in supplying components for construction of the 3,700-mile natural gas pipeline being built from Siberia to Western Europe. But there is no indication that an agreement is imminent. Reporters were told that the Europeans and Japanese were enthusiastic at first about proposals put forth by Secretary of State George P. Shultz in discussions with them earlier this month, but that their governments seemed to have trouble agreeing on explicit statements that could lead to an end of the pipeline dispute.

The United States said today, on the eve of a meeting between President Reagan and an Arab League delegation, that if the Arabs wanted a Middle East peace, they would have to agree to negotiate directly with Israel. In a policy statement read aloud at a briefing, a senior State Department official said Mr. Reagan would tell the Arab leaders on Friday: ''We believe the time has come to stop talking about talking about peace and start sitting down at the table, negotiating directly between Israelis, and Arabs, and the United States, and start achieving Palestinian rights, and start achieving the broader peace which is the key to the stability and security for Israel.'' The official, a senior aide to Secretary of State George P. Shultz, repeatedly stressed that the Administration wanted the Arab League to meet Mr. Reagan's request, set forth in his Sept. 1 Middle East initiative, that Jordan and the Palestinians of the West Bank and Gaza Strip join the negotiations with Israel, Egypt and the United States on self-rule for the Palestinians. 'The Central First Step' ''Our view is that the central first step is that the Arabs agree to support an early move of King Hussein to the table,'' the official said.

The lights dimmed in the auditorium, the slide projector whirred and the rectangular chart projected onto the large screen could be fairly described as a dispassionate version of the apocalypse. ''If there were to be a nuclear attack of 65 megatons - which is the scale used by the Federal Emergency Management Administration for civil-defense planning - within minutes about 83 million would be dead and 134 million would die before the month was up,'' said Dr. Herbert Abrams, professor of radiology at Harvard Medical School and an active member of Physicians for Social Responsibility, an antinuclear group. Dr. Abrams's lecture, which he delivered in an even, unemotional voice, took place at the first Conference on the Fate of the Earth, which ended yesterday at the Cathedral of St. John the Divine. Altogether, some 800 people from as far away as Stockholm and Seattle crowded into the cathedral's wood-raftered synod house and into various rooms at nearby Columbia University for workshops, speeches, exhortations and sober lectures like that by Dr. Abrams.

With many contests for Senate, House and governorships tightening in the homestretch of the 1982 political campaign, and large numbers of voters still undecided, the prospective voter turnout has become an increasingly important factor for both major parties. Republican and Democratic campaign managers and poll takers around the country report large blocs of undecided voters, sufficient to turn what are expected to be modest Democratic pickups in the House of Representatives into more significant gains if there is a late swing toward the Democrats. In many close races, campaign managers are saying the turnout level will be the key to the outcome. So far, Democratic and Republican political specialists say they have not detected a broad mood of protest against President Reagan and the Republicans that would increase the turnout and produce a Democratic landslide. Martin Franks, the executive director of the Democratic Congressional Campaign Committee, has forecast a gain of 15 House seats for the Democrats, about average for the party that does not hold the White House in a Congressional election in the middle of a new President's first term. Representative Guy Vander Jagt of Michigan, the Republican Congressional campaign chairman, contends his party will gain seats this fall. But David Gergen, a White House spokesman, said today that the White House would regard it as ''a major victory'' if Republicans ''come up on the sunny side of 20'' lost seats in the House.