What was going on when I was born?

WHEN Janet Holmes made plans to move from her large house to an apartment in Westchester, she did what many people do these days. Even before calling the moving company, she telephoned the tag-sale professionals. ''I had a houseful to sell, and I knew I couldn't tackle the job without help,'' she recalled. ''I didn't know enough about pricing or how to set up a sale or attract customers. Besides, I didn't want to watch while people commented and pulled apart the things I've lived with and loved for years.'' The sale, it turns out, was a success. Not only did she net a few thousand dollars more than she expected but she even disposed of some items that weren't on sale. ''People actually bought boxes of rusty nails and a pile of grocery bags I earmarked for the trash,'' Mrs. Holmes said.

Businesses increased their inventories by four-tenths of 1 percent in December, but sales rose six times as fast to a record level, the Commerce Department said today. With sales rising so much faster than inventories, the closely watched inventory-to-sales ratio - the amount of time it would take to use up available stocks - fell to a new low of 1.31 months. The ratio had been 1.34 months in November.

IT'S tough, said 25-year-old Alix Phillips, who moved here from San Francisco less than two years ago. The phrase is echoed by most of the young men and women who are beginning their careers and are ensconced in their first New York apartments. It's tough, primarily, to pay the rent, even for college graduates earning more than minimal salaries. Their housing is usually a disproportionate percentage of take-home pay. And because it almost always eats up a third or more of their salaries after taxes, financial leeway for day- to-day expenses and furnishings is limited.

IT used to be taken as read that French gardens were severe and mathematical. Paradigms of logic and order, they were places in which nature was forbidden to go her own way. Ruler and protractor had gone to work at an early stage, and an invisible but very large labor force made sure that those geometries were kept in perfect shape. Gravel was raked several times a day. Hedges took on the forms of cone and cylinder, obelisk and cannonball. Borders were trimmed to within a fraction of an inch. Chance was outlawed and every shadow knew its place.

A man free on parole after a manslaughter conviction was arrested in a Bronx hospital early yesterday and charged with murdering a New York City police officer and wounding two others. The officers were shot Tuesday night in the driveway of a Bronx gasoline station after two of them, getting out of a patrol car, tried to question the man about the theft of a moped, according to the police. One of the officers, 30-year-old Thomas P. Ruotolo, was slain with a single shot to the head at a range of less than five feet. His partner, Tanya L. Brathwaite, 23, responded with a single shot from her service revolver, but she fell to the ground with a bullet in her lower back.

The International Business Machines Corporation will market its first portable computer within a month, according to dealers who said they were notified Monday to expect the machine. Details of the portable, which would mark a significant addition to I.B.M.'s home and personal computer line, were sketchy yesterday. But the retailers, who refused to be identified because I.B.M. made them agree not to disclose the existence of the machine, said they expected it to sell for about $3,000.

Because of an editing error, a front- page article in some editions yesterday incorrectly described Federal regulations concerning the pesticide EDB. The Government still requires the use of EDB on certain imported fruit.

The State Public Service Commission today voted to divide New York City into two area codes to ''prevent an impending exhaustion of telephone numbers.'' Beginning New Year's Day, the 212 area code will reach only telephones in Manhattan and the Bronx. A new area code, 718, will be required to call Brooklyn, Queens and Staten Island. The decision set off an outcry from public officials, including threats of suits and calls for legislation. The officials argued the change would divide the city, hurt the development of business, cause confusion and stigmatize Brooklyn, Queens and Staten Island.

Ethel Merman, the musical-comedy star whose belting voice and brassy style entertained Broadway and movie audiences for 50 years, was found dead in her Manhattan apartment yesterday. Miss Merman, who was 76 years old, had undergone surgery to remove a brain tumor last April. The Medical Examiner's office reported yesterday that she died of natural causes. The singer's booming voice was first heard on a Broadway stage in 1930 when she brought down the house singing ''I Got Rhythm'' in the Gershwin musical ''Girl Crazy.'' Her last major appearance in New York was in 1982, when she took part in a Carnegie Hall benefit concert.

The Justice Department said today that it would sue to block a proposed merger of the LTV Corporation and the Republic Steel Corporation - the nation's third- and fourth-largest steel companies - unless they dropped the plan or significantly changed it. J. Paul McGrath, Assistant Attorney General in charge of the department's antitrust division, said the division opposed the merger because the resulting combined company would control too large a share of a market in ''critical parts of the steel industry where only a few domestic companies compete.'' That would create ''a risk of increased prices through collusion,'' Mr. McGrath said in a news conference. Analysts and steel executives said today's decision would force the industry to find other ways to achieve its goals. (Page D4.)

The American director general of the multinational force in Egypt's Sinai Peninsula was fatally shot here tonight as his car approached his apartment. The director, Leamon R. Hunt, who was 56 years old, died at San Giovanni Hospital an hour after being hit by bursts of bullets from automatic weapons. His Italian chauffeur, who was unhurt, reportedly told the police that two men of olive complexion had made the attack but that only one had actually fired. Mr. Hunt was on his way home at the time from the headquarters here of the 10-nation multinational force, which includes 800 American soldiers. The force was set up in 1981 to monitor observance of the Israeli-Egyptian peace treaty, which provided for the return of Sinai to Egyptian control. The peace treaty was an outgrowth of the Camp David accords of 1978.

For major stock groups, the market's plunge in the last five weeks has brought mostly gloom, but there have been slight glimmers of light here and there. The worst performing stocks - almost without exception - have been those that had performed the best in the early days of the bull market. Building materials companies, appliance manufacturers, savings and loans and other ''interest sensitive'' businesses tied to the housing industry have rapidly fallen from favor. Likewise, large electronics and computer companies, aluminum manufacturers and transportation companies that saw their stock prices rise steadily last year have fallen back.