What was going on when I was born?

International Israel's new Defense Minister is to be Moshe Arens, the Ambassador to the United States, who, like the outgoing Defense Minister, Ariel Sharon, holds hard-line views on key aspects of Israeli policy. Mr. Arens's appointment, announced by Prime Minister Menachem Begin's office, is expected to be approved by the Cabinet and Parliament. (Page A1, Column 6.) The small Persian Gulf states are increasingly concerned over falling oil prices. For the first time since the big price spurt in 1974, the conservative, pro-Western rulers of Kuwait and the other vulnerable oil-producing countries are learning that they can no longer count on constantly rising revenue to buy domestic peace. (A1:5-6.)

''Internal developments in Israel do not have - and will not have - any impact on the process of peace in the Middle East.'' - Menachem Begin. (A8:1.)

Some homeowners may be hit with an unexpected tax liability this year. When interest rates were rising, many banks offered to buy back low-interest mortgages from their customers at a substantial discount. The difference between the outstanding mortgage and the amount paid to cancel the debt could be considerable - and it is taxable income. ''When the banks came around and said, 'You have outstanding a $60,000 mortagage at 5 percent, but if you give me $40,000, I'll consider it paid off,' most people didn't realize they would be taxed on the difference,'' said Gail Winawer of Oppenheim, Appel, Dixon & Company, an accounting firm. ''But that's $20,000 of taxable ordinary income.'' Home ownership usually creates a tax liability only when a dwelling is sold for more money than it cost. With planning, though, it is often possible to defer taxes on such capital gains. If you are buying or building a new home that costs at least as much as the sales price of the house you are leaving, the entire gain can be deferred until the new home is sold. But this deferment - or rollover, as it is often called - is lost if the new residence is not bought and occupied within 24 months of the sale of the old residence.

Congressional Democrats said today that they would accept a $4.3 billion emergency jobs bill proposed by the White House as a starting point in dealing with unemployment. But they said they would try to add about $1 billion to the measure. The Democrats said that the emergency package was only ''phase one'' of their efforts to deal with high unemployment and that they would propose other initiatives in future months. ''We don't think it goes far enough,'' Representative Thomas S. Foley of Washington, the Democratic whip, said of the White House plan. ''The Democrats accept it as the first phase, not as the final and complete resolution of the human needs that exist in society.''

There seems little doubt now that the Washington Public Power Supply System will be unable to meet a $15.7 million monthly interest payment to the Chemical Bank on March 31, credit market analysts agree. At that point, the nation's largest issuer of tax-exempt bonds would lapse into technical default on $7 billion of principal and interest on bonds issued for two abandoned nuclear power plants. What is not clear, and nowhere near resolution, is how deeply its suppliers, bondholders and Wall Street municipal bond underwriters will suffer if one or more of them force the supply system into default. Although a few 11th-hour efforts are under way to avert a default, many analysts say it is highly likely to occur before the end of this year. ''People have misperceived the severity of the problem for too long,'' said Eileen Titmuss, a bond analyst with Drexel Burnham Lambert Inc. ''The search for a last-minute solution will be very problematic, if not impossible.''

Former State Senator Vander L. Beatty of Brooklyn was indicted yesterday on forgery and other charges stemming from his unsuccessful attempt to win a 1982 Congressional primary. He was accused in the state indictment of having instructed political aides to put false signatures of voters on voterregistration cards while he and the aides were in the Brooklyn office of the city's Board of Elections some time in October. In addition to the forgery charge, Mr. Beatty was indicted on charges of criminal conspiracy and election-law violations. According to the Brooklyn District Attorney, Elizabeth Holtzman, who announced the indictment, Mr. Beatty and his associates were involved in a post-primary effort to create ''irregularities'' that would lead a court to throw out the results of the primary and order new balloting.