For Eastern Europeans, historical anniversaries are not academic affairs. They are front-page news, a coded commentary on the present, when anger explodes and deep feelings are revealed. The ``news'' here these days is the Aug. 20, 1968, Soviet invasion of Czechoslovakia and the creation in Gdansk of the independent trade union Solidarity on Aug. 1, 1980. About 10,000 Czechoslovaks demonstrated Sunday in Prague chanting, ``We want freedom. Russians go home,'' while Polish workers in Gdansk's shipyard yesterday joined striking coal miners by walking off their jobs in support of Solidarity.
Meticulous official preparation could not prevent the outburst. In the days before the Aug. 20 anniversary, Czechoslovak newspapers ran daily articles explaining how ``fraternal assistance'' was needed to squash the 1968 Prague reforms.
``When we were drawing up the basic outlines of our news coverage this year, one of the priorities was the anniversaries,'' says Jiri Kohout, a senior editor at the Communist Party daily Rude Pravo. ``History is here to teach lessons.''
Mikhail Gorbachev's ascension to power has given new meaning to these lessons. The Soviet leader has begun to revise long-accepted tenets about his own country's past, and East Europeans have great expectations that he will do the same for them.
So far, Mr. Gorbachev has disappointed. He has not yet disavowed Soviet intervention either in Hungary in 1956 or in Czechoslovakia in 1968. Nor has he objected to the declaration of martial law in Poland in 1981, which led to Solidarity's banning.
East Europeans hold two theories why such admissions are so difficult to make. Cynics claim Gorbachev merely is an enlightened czar who wants to reform Russian society while keeping firm control over his empire.
``Although I have great sympathy for the changes taking place in the Soviet Union, we must be under no illusions,'' cautions Solidarity activist Bronislaw Geremek. ``For all his perestroika and glasnost, Gorbachev means to guard the old imperial order.''
Optimists believe that the dynamic Soviet leader just needs more time. They say he is still not strong enough to take on Kremlin conservatives about sensitive historical events in Eastern Europe.
``Although it may take some time yet,'' says Jiri Dienstbier, a founder of Czechoslovakia's Charter 77 human rights group, ``Gorbachev eventually will come to realize that his `new political thinking' hardly can be credible if it is not supported by convincing behavior toward the suppression of the Prague Spring.''
Discussions of East European history always have tended to be contentious and emotional. ``Unlike you Americans, we could never take for granted the existence of our nation,'' says Jan Kren, author of three books on German-Czech relations. ``It's this special Middle European quality that makes our historical memories so powerful.''
Communist rejection of Western-style debate aggravates this tension. Marxist theory holds that history hides ideological lessons, and there is a ``correct'' and ``incorrect'' version of an event. The observance of an anniversary - official or unofficial - takes on emotional overtones.
Solidarity supporters marched in Gdansk two weeks ago to recall the founding of their union. Some 10,000 Hungarians chose the date of the 1848 Revolution to parade through Budapest chanting ``Democracy, Democracy!''
This year's most fateful anniversaries are in Czechoslovakia. In March, the Communist Party celebrated the 40th anniversary of the communist takeover in Czechoslovakia. In September, there will be the 50th anniversary of the 1938 Munich Agreement, which led to Adolf Hitler's occupation of the nation. The lesson here is clear: Don't trust the West. The following month, the Prague leadership hopes to revive patriotic feelings by celebrating the 70th anniversary of the creation of the Czechoslovak state in 1918.
``These official celebrations are comedies,'' complains historian Kren, a Charter 77 signer. ``The communists are rehabilitating the old Bourgeois Republic in hopes of benefitting from its prestige.''
Milos Jakes, the new Czechoslovak leader, was a Moscow loyalist in 1968 who opposed the Prague Spring reforms, and in 1969, as chief of the Central Control and Audit Commission, he played a key part in the purge which swept half a million people out of the party. Many of these ex-party members dream of returning to positions of influence, including former party General Secretary Alexander Dubcek, now a retired forestry official living in Bratislava.
Sunday's demonstrators chanted ``Dubcek, Dubcek.'' In numerous interviews granted this spring, Dubcek suggested that he may soon be rehabilitated.
That surely is too optimistic. Mr. Kohout dismissed Dubcek and his friends as ``relics of history.'' In private, Prague's rulers say they fear losing their own positions. ``Remember, [French President Charles] de Gaulle was in retirement 12 years, and everybody says he was through,'' says one official. ``Then all of a sudden, times changed, and he had the whole nation behind him.''
``The anniversaries raise expectations which scare the government,'' a Western diplomat says. ``If Jakes and the present leaders want to make a change, I'm almost sure they'll wait until after 1988 when they are not so preoccupied with the past.''