Tomorrow is the day the William Shakespeare put on the map: the Ides of March.

It is a phobic day, closely associated with the verb, "beware". Shakespeare apparently planned it that way, working the expression, "Beware the Ides of March" three times of dialogue in "Julius Caesar," Act I, Scene II. Caesar didn't beware and a few minutes later he was under the knife.

Perhaps because of Shakespeare's sponsorship, idophobia is a highly specialized alliftion; it is limited almost exclusively to English-speaking countries and, even there, to people who have read Shakespeare. Your average browser of Marvel Comics probably doesn't know what an ide is, let alone why anyone should be afraid of it.

One reason to be afraid is that the ides are confusing. The term comes from the Latin word meaning to divide, and still conceals itself in the English word. In the calendar of the Roman Republic, the ides were the middle of the month -- generally the 15th, since months tended to have approximately 30 days. But the term could be applied roughly to days around the middle of the month. They were originally intended to coincide with the full moon, though that happened only occasionally, because the Romans were not very good calendar-makers.

If we take the ides to mean roughly the middle of March, say from the 14th to the 16th, there is plenty to beware and even more just to note as a curiosity. But March 15th, except for Shakespeare's passing obsession and Caesar's passing, seems to have become one of the less fright-filled days of the year, perhaps because people have been busy bewaring.

It is not a day totally without distinction, to be sure. This year, it marks the beginning of National Poison Prevention Week, and in Hinckley, Ohio, March 15 is known as Buzzards Day. It is the day the buzzards return to Hinckley (like the swallows at Capistrano four days later) from their winter home in the Great Smoky Mountains. (This information may be found in Chase's Calendar of Annual Events, which is a dandy reference work for people who want to seem omniscient.)

Bewaring is in the eyes of the beholder. Some events of mid-March might start Ronald Reagan quoting Shakespeare while others would find them welcome. There was a resumption of SALT meetings in Vienna on March 15, 1971, for example, and the Senate passage of the Panama Canal treaties in 1978 -- but that began on March 16.

One spectacular near-miss, if you want to pin the ideas down strictly to the 15th, is the My Lai Massacre -- March 16, 1968. There are plenty of contenders if you stretch it that way. Take 1976, for example.On March 14, Anwar Sadat abrogated the 1971 treaty of friendship and cooperation between Egypt and the U.S.S.R. In 1978, Aldo Moro was kidnapped in Rome and the Soviet cosmonauts returned to earth after 96 days in space in the Soyuz 27 capsule -- but these things happened on March 16. The most important thing to be reported on the 15th was "U.S. coal strike nears settlement." There was also an airliner crash near Sofia in which all 73 persons on board were killed -- but that, too, was on March 16.

Speaking of air disasters, March 1980 had a rash of them: In Turkey, 18 people were killed -- all Americans; in Poland, 87 died, including 22 Americans. Both disasters were on March 14.

March catastrophes a year earlier also tiptoed past the ides. In China, a military jet crashed into a factory, killing 44 people, and in Qatar, a Jordanian jet crashed, killing 45. Both accidents happened on March 14, as did a crash between a Greek bus and a Yugoslav gasoline tanker truck near the border between the two countries. The death toll of that accidnet was 30, with 22 injured. Later, there was a nursing-home fire in Norway that killed 11 people -- but that was two days later, on March 16.

Then there was the great blizzard of 1977, which closed more than 100 miles of interstate highway and killed nine people in Colorado, four in Nebraska and two in Kansas.But it took several days to dl all that, and March 15 was only one of them.

There have been ominous ides without a doubt -- the Ides of April 1920, for example, saw the robbery in Massachusetts for which Sacco and Vanzetti were executed many years later. But that would be a month late to do Shakespeare any good, though he might have made an interesting play out of the story. Even when they happen in March, modern disasters seem to avoid the ides -- the Three-Mile Island emergency, for example, which began on March 28, 1979.

What do you get on the ides? In 1972, for example, Congress approved a temporary increase of $20 billion in the national debt ceiling, raising it to $420 billion. The increase was, as mandated, temporary. The ceiling is now $985 billion.The 15th is a Sunday this year, so one perennial victim of massacres in March -- the national budget -- has a day of grace. But beware, the knives will be out again on the 16th.