What was going on when I was born?

NO longer are retirement communities looked upon by the elderly as ''old-age homes.'' More and more Americans of advanced age are moving into them, social researchers say, not to withdraw from active life in their later years, but for the positive support of others like themselves. An awakening of ''aging group consciousness,'' of group pride and feelings of self-worth among the elderly, is perhaps the most important of the findings of social scientists and researchers investigating the still-new field of retirement living, a field that until recently was without basic statistics. Until a private research study by University of Michigan investigators was published 21 months ago, it was not even known how many retirement communities there were in the United States, much less precisely who was living in them. Today's best estimates are that about 924,000 people now live in 2,363 nongovernmental retirement communities throughout the country and 600,000 others are in retirement housing provided under United States Department of Housing and Urban Development programs, a small but significant portion of the estimated 27 million Americans 65 years old and older. And sociologists who study housing patterns of the elderly expect that even more people will move into such communities as life expectancies increase and the older population expands.

President Reagan, saying a rise in the use of chemical weapons had ''serious implications for our own security,'' announced tonight that the Administration would propose a treaty this month to ban the production, possession and use of such weapons worldwide. In an opening statement at his televised news conference, however, Mr. Reagan asserted that the United States needed a ''limited retaliatory capability of its own'' in chemical weapons to deter what he charged was a ''massive arsenal'' built up by the Soviet Union in recent years. Mr. Reagan said that ''only an effective monitoring and verification package'' could insure compliance with the treaty, and that he would propose ''bold and sound verification procedures'' along with the treaty. He offered no details. 'Mandatory Inspections' Required A senior Administration official said the draft treaty would require ''mandatory inspections'' of chemical weapons production sites that have been declared to exist, as well as ''a right to look at suspected undeclared production sites.''

SPRING is traditionally a time for sprucing up around the house. Outside and inside chores that have been put off during the winter months - some because of weather, others because of inclination - are best done now, in the warmer weather. A good way for a homeowner or apartment dweller to begin a spring fixup program is to make a checklist of potential trouble spots and to note for the future all the chores to be done each year at this time. This easy-to- follow checklist can be a guide: Around the Outside Siding Take a slow walk around the house with a note pad to see if the siding needs painting or repairs. If the siding is in bad shape or has frequently needed repainting, it might pay to replace it with vinyl or factory-finished aluminum siding. Vinyl will never need painting, and aluminum won't for many years.

Huge demonstrations today paralyzed the eastern part of France, where the Government plans to eliminate 25,000 jobs from the ailing steel industry. Protesting marchers brought traffic to a standstill in the streets, and angry workers blocked highways and railroads with heavy coils of sheet steel and piles of burning truck tires. Facing the broadest worker resistance to his policies so far, President Francois Mitterrand refused to soften his actions.

''The street disappeared. Then the smoke settled down, and there was nothing there.

The Ford Motor Company's newest automobile, scheduled to be introduced in September, will not be a Ford, a Mercury or a Lincoln. It will be a Merkur (pronounced mare-COOR), a separate car line the company is establishing in an effort to appeal to buyers who otherwise prefer, and can afford, the European sedans sold by BMW, Saab, Volvo and Mercedes-Benz. The Merkur will be the first car since the ill-fated Edsel of the 1950's that Ford has brought out in this country without the Ford, Lincoln or Mercury nameplate. (It could be noted, however, that Merkur is the German word for Mercury.) And Ford acknowledges that it is going counter to conventional marketing wisdom in choosing a name that people will inevitably mispronounce.

The military junta that seized power in this West African nation on Tuesday vowed in a communique issued today to encourage free enterprise and uphold human rights. As the military made its announcement, life appeared to return to normal in this city of once-graceful colonial buildings ravaged by years of harsh weather and neglect. Groups of people waited patiently in the wilting heat for delapidated, overcrowded buses or shopped at the metal- roofed stalls in the city's marketplace. At times people cheered or waved to cars and trucks carrying soldiers, but the majority of the residents showed little interest. 'Too Soon to Say' ''This is perhaps a good thing that has happened,'' said a man who identified himself only as Mr. Camara, a common name here. ''But it is too soon to say.''

The governors of the six New England states met privately today to discuss how to cancel the No. 2 unit at the Seabrook, N.H., nuclear plant, but resolved instead to study whether both units should be canceled. Gov. J. Joseph Garrahy of Rhode Island, chairman of the New England Governors Conference, and others at the meeting, which was held at the Providence, R.I., airport, said they feared that Seabrook 2 would drag Seabrook 1 down with it. In an interview with reporters after the meeting, the governors said they have asked a consultant to prepare, within three weeks, a study on the Seabrook project. Governor Garrahy said the study would ''examine the whole liability of Seabrook.''

News Analysis The black vote for the Rev. Jesse Jackson in Tuesday's Presidential primary marked what many Democratic leaders described yesterday as a turning point in New York politics. After capturing 34 percent of the city vote and 26 percent statewide, Mr. Jackson declared Tuesday night: ''Chicago had its time. Philadelphia had its time. New York, your time has come!'' With Mr. Jackson carrying his campaign to other states, black leaders here were trying to assess whether New York would follow the lead of Chicago and Philadelphia by electing a black mayor next year.

Jesse Jackson's strong showing marks a turning point in New York politics. News analysis, page B1. Voter survey shows strong support for Governor Cuomo, page B10. PHILADELPHIA, April 4 - The three Democratic Presidential candidates swept into Pennsylvania today, tailoring their campaigns here to the lessons of New York and the demographics of this economically distressed state.

Of the 524 students on athletic teams at the Hopewell Valley Central High School here, 245 are girls and 279 are boys. The $21,000 budget for sports equipment is divided equally between the sexes. Freshman girls have two sports; boys have two. There are five junior varsity teams for each sex and 10 varsity for each. And the girls' teams have done well in interscholastic competition. Better, in fact, than the boys' teams.

President Reagan, entering the third month of his re-election campaign, challenged Congress tonight on a broad array of foreign and domestic issues. Mr. Reagan, in a nationally televised news conference, repeatedly criticized Congress for its role on such issues as Lebanon, El Salvador aid, restrictions of the War Powers act, public school prayer, his fairness toward the poor and the ''sleaze factor'' charges being lodged against his appointees by Congressional Democrats. The President, less than a week after withdrawing forces from the coast of Lebanon, said flatly that Congress ''must take a responsibility'' for events in Lebanon. More than 260 Marines died during the President's controversial commitment of American troops to a multinational peackeeping force in Beirut. A Complaining Tone Mr. Reagan described in a clearly complaining tone the Congressional debate on the topic, '' 'Oh, bring our men home, take them away,' '' and declared: ''All this can do is stimulate the terrorists and urge them on to further attacks.''