Forget all those other divisions for the world - the rich and the poor, the beautiful and the ugly, the bright and the dumb. The ultimate demarcation for humankind is time, as in those who are on time and those who aren't.

It is a rift that has no common ground between sides. Marrriges have foundered over it, friendships been strained, contracts lost, and planes missed. And nowhere is the breach between the two sides of time so clear as in Washington, a city that runs by the clock through a maze of early-morning briefings, luncheon meetings, right into cocktail gathering and dinner chats.

Even the chief resident of 1600 Pennsylvania, Jimmy Carter - himself a fiend about puntuality - has to contend with the division. Press Secretary Jody Powell is so notoriously late for the early-morning staff briefing that the President has been known to quip, "Nice of you to join us."

"Both Hamilton (Jordan) and Jody are like the airlines," says one White House correspondent. "If they're 30 minutes late, they're on time. It's usually worth the wait, but they're so frequently late for appointments that I always call their secretaries 15 minutes before an appointment to see if it's still on."

In the press of government business, its' understandable how someone could be late. Yet Carter himself is rarely off schedule. White House appointments secretary Tim Kraft always interrupts meetings with the President five minutes before the time is up by coming in with an index card for Carter. This is a signal to the President that the time for the interview has run its course.

And, of course, "People aren't habitually late to see the President," says Kraft.

Still, there are different kinds of timeliness. In society, being on time is different from punctually in the government.

Take the 8 o'clock dinner party, for example. Arriving at 8, one is not on time, one is early. Fifteen minutes after the hour is on time.

"It's the acceptable academic quarter of an hour lateness," says socialite Ina Ginsberg, head of the Friends of the American Film Institute. "I think it must have been the Americans who started this thing about being on the dot for everything. In Europe, people aren't expected to be punctual. I never am and when I have to be it's a real struggle."

Indeed, at embassy functions, there are times when one is supposed to be late, or, rather, later than one's host. Chief of Protocol Evan Dobelle recalls a Saudi Arabian reception for Crown Prince Fahd. The Crown Prince was running late, but "Vice President Mondale was alreadyen route and would have gotten there before him, which isn't done. We contacted the Vice President and told him the situation and he said it was all right, he'd have the car pull over to the curb and do some paperwork so that it would give time for the prince to arrive first."

In less official circles, though, it is a struggle for those who are always on time to bring themselves to understand those who aren't.

After several dates with a woman who always arrived late and breathless with apologies, one local psychiatrist confronted the culprit to see if this was going to be a trend in their relationship. The woman explained that she never arrived on the dot, that 15 minutes after an appointment was standard operating time. The man wrung his hands, imploring the netherworld and cursing his fate. "Why am I always falling for women who are not on time? I hate it. I hate it."

Needless to say, the relationship did not prosper. But always being on time is not necessarily a healthy trait, according to Dr. Leon Salzman, professor of clinical psychiatry at Georgetown University School of Medicine. "It can be a compulsive behavior, a kind of ritualistic performance that helps you feel secure and like you've got control of your life. People who are always on time view it as a measure of their worthwhileness, their status depends on perfectionism."

Equally, says Salzman, those who are always late are following a security ritual. The late Marilyn Monroe was a legendary laggard, a habit that was viewed as a sickness. She was so often that production on her last picture, "Something's Got to Give," was halted because her tardiness interfered with the film's shooting.

But, of course, for most movie stars and other luminaries, there is the grand entrance - something one has to be late for, otherwise there is no audience to see it.

Arriving late for an interview in the Polo Lounge of the Beverly Hills Hotel, Groucho Marx once made a satire out of the grand arrival. Wending his way through the crowded room, he stopped to speak to half the women in the lounge. "I'm sorry I was late," he announced to each. "I was trying to get a date. I'll take her to the movies. I get in all the movies free. I'm Groucho Marx, the living legend." The performance delighted the other diners.

For those who aren't consistently late, but seem to arrive more late than on time, Salzman says, "They have so many things to do that they view time as endless. They are not being insulting or inconsiderate when they're not on time, they just have a different way of looking at time."

And those who are determined to be late, will be. Compensating for their lateness won't work for long: They compensate for the compensation. When friends consistently arrived late for one hostess' dinner parties, she tries telling them that the affair was a half-hour earlier. They soon caught on to the ruse, and started arriving an hour after the given tiehe ruse, and started arriving an hour after the given time.

Even joking about someone's lateness won't necessarily alter their ways if they've got the habit.

Walter Hopps, curator of contemporary art for the National Collection of Fine Arts, had such a reputation for dawdling that staffers decided to rib him out of the habit. One of them commissioned a number of white buttons with "Walter Hopps will be here in 20 minutes" printed on them for staffers to wear instead of answering repeated questions about where he was.

Up on Capitol Hill, punctuality can be thrown into havoc by a crowded schedule. "Last Friday, there were a lot of things going and Sen. Edward Kennedy (D-Mass.) ended up running behind by about 30 minutes by 3 in the afternoon," said one of Kennedy's staffers. "It totally depends on what is happening during the day and a 14-hour day is nothing unusual.

Perhaps, though, as Ginsberg implies, punctuality is a particularly American trait.

African writer Chinua Achebe, in Washington once to speak to a group of college journalism majors, arrived more than fashionably late. He did not apologize. Instead he gave the students a dissertation on concepts of time, ending it by saying, "Now you were worried about me getting here on time. I was worried about getting here at all."

Even Carter, for all his punctuality, is frustrated by time periodically.

About three months ago, Carter as supposed to meet with a group of editors at 1 o'clock. At five minutes till the hour, the White House press of fice hustled photographers and reporters into a corridor outside the Cabinet room where Jody Powell was extemporizing befor e the editors until the President arrived.

The appointed hour came and went. Five minutes after the hour, ten minutes, 15 minutes. Powell sent someone to see what was up; the reporters began to get restless, wondering whether some national disaster or momentous event was keeping Carter occupied.

There were mumblings about calling offices, checking with editors, scanning the wires, when suddenly someone began to push against the crowd crammed into the doorway. The group called out to stop pushing, to be quiet because they were waiting for the President. A voice chimed back, "I am the President."

The crowd parted and Carter swept in.

"He never missed a beat," recalls on admiring staffer. "But actually, he'd just forgotten the appointment and gone to have lunch."