What was going on when I was born?

J. Lynn Helms, the Administrator of the Federal Aviation Administration, submitted his resignation today, saying he wanted to resume his business consulting work. President Reagan accepted the resignation expressing regret and thanked Mr. Helms for a ''job well done.'' Mr. Helms's handling of the 1981 air traffic controller's strike was, as President Reagan said in his brief letter of acceptance today, his best-known accomplishment. Mr. Helms, with the backing of the President, dismissed 11,400 strikers of the Professional Air Traffic Controllers Organization and kept the nation's airports open, though at a reduced level. The exchange of letters between Mr. Helms and President Reagan made no mention of reports that Mr. Helms's private business dealings had been under investigation.

The State Department has recommended that President Reagan file notice that the United States will withdraw from Unesco in 1985 unless the United Nations agency curtails what the Administration regards as questionable political activities. The recommendation has been sent to the White House, according to a State Department official, with the President facing a deadline of Dec. 31 for deciding whether to send formal notice of withdrawal. If he does so, according to Administration advocates of the recommendation, he would then have a year to continue American participation in the agency while applying leverage for changes.

After years of hand-wringing over the ''holiday blues,'' a form of depression once thought to afflict vast numbers of Americans, mental health experts now stress that Christmas actually intensifies most major emotions of everyday life, joyous or sad. Christmas is a time, they say, when lovers rejoice more than ever while the lonely may sink into despair; when close-knit families bind together while warring households shatter; when most workers relax and enjoy themselves while workaholics fret and feel guilty, and when the mentally well may feel better while the mentally ill may feel worse. Christmas is also a time, they say, when dimly remembered roles are resumed with new intensity as far-flung families reunite. Sibling rivals who live a continent apart may return home to compete again for a favorable nod from their parents, and powerful professionals who command respect and awe in the community may find themselves reduced to whining children under the disapproving glance of a dictatorial mother. For Most, No Despair But for most people Christmas is not a time of depression and despair, according to the handful of researchers who have studied the psychological impact of the season.

Lance Cpl. Russell Biffle, from Mississippi, watched today as Bob Hope told jokes, Brooke Shields burst into song and Cathy Lee Crosby cavorted in a slinky red dress. It was, he thought, like getting at least a little bit of America in the tormented country of Lebanon. ''It's not home,'' Corporal Biffle said after the Hope Christmas concert aboard this 18,500-ton helicopter assault ship, 10 miles off Lebanon, ''but it's as close to home as we'll get.''

President Sandro Pertini said Italy should withdraw its military contingent from Beirut. Page 4. WASHINGTON, Dec. 23 - The Defense Department today postponed publication of a report on the truck bombing of the Marine compound in Beirut amid indications that the Reagan Administration is divided over how to deal with the document. A Pentagon spokesman, announcing the delay 30 minutes before copies of the report were scheduled to be given to reporters, said Secretary of Defense Caspar W. Weinberger needed more time to review the document and prepare recommendations for President Reagan.

Mail service in New York City has gone through its worst year of delays since 1980, according to United States Postal Service figures, but officials say the problems abated in time for improved Christmas deliveries. ''We had some slippage,'' George F. Shuman, the postmaster of New York, acknowledged. He attributed the decline in service to disruptions from automation and route realignments and to a 10 percent increase in mail volume, now running at about 6 billion pieces a year in the district. But Mr. Shuman said Postal Service figures indicated that service had improved in recent weeks and that deliveries this Christmas were speedier than last year. Service Is Put to the Test In a test whose results were reported this month, members of the New York Society of Association Executives mailed 363 letters to each other in Manhattan last July. The group said 152 letters reached their destinations by the next business day, 77 in two days, 30 in three days and 27 in four days or longer. Another 77 letters disappeared altogether, the group said.

Pope John Paul II said today that the deployment of more nuclear missiles in Europe worried people on the continent, and rightly so. ''A new and grave uneasiness fills public opinion, and I understand it,'' he said in a message prepared for the 17th ''World Day of Peace'' on Jan. 1.

The United States and Rumania signed an agreement on cooperation in science, education, television and other fields, the United States Information Agency announced today. The two countries have had such agreements for 10 years.

Two major political meetings next week may help dispel uncertainties that have surrounded the leadership of Yuri V. Andropov since he fell ill and disappeared from public view more than four months ago. Eastern European officials here are saying Mr. Andropov is sure to appear at a full meeting of the Communist Party's Central Committee that is to begin in closed session Monday or Tuesday. These sources have been less emphatic about the meeting of the Supreme Soviet, the nominal legislature, which is scheduled to convene in public session Wednesday. The meetings are usually held in November, and there is little doubt that Mr. Andropov's illness was the reason for the unusually long delay this year. When the date for the Supreme Soviet was finally set late last month, the Kremlin seemed to have concluded that Mr. Andropov, who is both party leader and Chairman of the Presidium of the Supreme Soviet, was either too ill to have any prospect of attending or recovering well enough to plan a return to public view.

''Ceau- ses-cu! Peace!'' people packed into the Grand National Assembly chanted, clapping their hands in rhythm. ''Ceau-ses-cu! Rumania!'' they chanted a moment later as President Nicolae Ceausescu paused in his speech to the nominal Parliament. Government employees, Members of Parliament, generals with gold-encrusted epaulets and what the official press described as ''leaders of the main institutions, veteran party members, workers and peasants'' all beat their hands together and shouted after every few sentences throughout the President's long oration. ''Ceau-ses-cu and the people!'' they chanted. ''Ceau-ses-cu and the Rumanian Communist Party!''

Heavy rain in the southern state of Tamil Nadu, over 15 inches in some areas, killed at least 26 people today and left thousands homeless, the Press Trust of India news agency said. Most of the deaths occurred when rain- soaked mud walls of houses and huts collapsed on their inhabitants, it said. The state capital, Madras, received 6.8 inches of rain, but that area is recovering from a drought and the water was welcome.

Jeanne Sauve, who was nominated today by Prime Minister Pierre Elliott Trudeau to be the first female Governor General of Canada, was once regarded as something of a political outsider by many of her male colleagues. That was three and a half years ago, when she was Canada's first Speaker of the House of Commons to be a woman. There was, some recalled, a palpable atmosphere of resentment toward her in the male-dominated lower house. The 61-year-old Mrs. Sauve was widely viewed as something of an outsider, a former member of the Cabinet with no great knowledge of procedural rules nor any close ties to the clubby fraternity that had administered the bureaucracy around Parliament.