A week is a clock, and Saturday night its chime. We may be modern, but we mark the sound.

In Nightingale's Tattoo Parlor on 12th Street NW, the mark is a tattoo in the shape of a rose.

The evening of the seventh day throws the most ancient shadow of all, the shadow of Saturnis Deis, Day of the Planet of Saturn, seventh from the sun. Cold and distant, 885,900,000 miles from the sun, it is still brighter in our sky than a first magnitude star. Baleful is the sign of Saturn, a chill to be dispersed by revels.

Bob Mater, the bartender at Timberlake's, warms to the night. "It's shooter time!" Bob may call you "'rabbit face," but it's all in fun, it's all in the rush toward midnight as the week winds down.

Saturn was the roman God of growth (Satus: corn), and in mid-December in Caesar's time, in celebration of the winter planting in Italy, the schools were closed, executions postponed, gambling with dice permitted, and the slaves freed to dine with their masters and freely speak their minds. The Saturnalia is weekly now, and the slaves who are freed are us.

At the Alexandria Roller Rink, a teen-age crowd circles at spped, running cool under the colored lights in a place where the night is always young.

On Saturday night there's nothing at all on TV. Oh, "Love Boat": but seldom a recent film, or special, or major sporting event, because the Nielsen ratings reveal that Saturday night is the night America goes out, and even the networks bow. "Saturday Night Live" was the exception, and fittingly. Chevy Chase mocking us all, making faces into the national mirror.

Saturday is a day of culmination, and it is capable of bad temperament. "Black Saturday" of Sept. 10, 1547: the Battle of Pinkie Cleugh (Somerset crushed the Scots, but with them the idea of Brittanic unity). "Black Saturday" of Aug. 4, 1621: the Ratification of the Articles of Perth. (Emboldened King James, who had already substituted the Episcopal for the Presbyterian form of church government, demanded kneeling at communion.)

The mood of Saturday's night can be darker still. It was then that the "dirty little coward" shot Jesse James. ("It was on a Saturday Night/If I remember right" the ballad goes.) It was then, in the Saturday Night Massacre of Oct. 20, 1973, Elliot Richardson and William Ruckelshaus followed Archibald Cox out Nixon's door.

A momentum seems to build. In music, when the end is in sight and the tempo quickens and the answer begins to overlap the subject (as in a fugue), that is called stretto. A week ends in stretto, with Saturday Night Fever and John Travolta dancing to the beat.

A slow build toward intensive dancing and sweating at Season's Restaurant and Nightclub, "a place that attracts a sophisticated group of people."

Wise folks try not to go out on Saturday night. (Yes, and Lawrence Talbert tried not to go out when the moon was full, but there he was anyhow, covered with hair and howling in the torchlight.) The lines at the movies houses are long, reservations are required for dinner, and the streets blaze with creeping headlights.

The slow dip of a doughnut on Old Georgetown Road, in a shop halfway between nowhere and home, where the foil ashtrays grow fuller as the night wears on.

"A time to weep, and a time to laugh; a time to mourn, and a time to dance." Was Ecclesiates, the kindly cynic, talking about Saturday Night? "Dead flies cause the ointment of the apothecary to send forth a stinking savor: so doth a little folly him that is in reputation for wisdom and honor." Was Ecclesiates talking about the time you put the lampshade on your head and quacked through the boss's party like a platypus? Some memories of Saturday Night never go away: they are narrated forever by a voice in the memory that sounds like Orson Welles and intones, in a puzzled tone, "No one to this day knows why he made such a fool of himself, no one to this day knows why. . ."

But we do know. It was Ecclesiastes' folly, danced to a little Saturday night music.

On stage at the Source Theatre, the actors play bickering spouses, and when the curtain's drawn, bicker on toward Sunday.

Ah, but we're immune -- you and me. Bright lights reduce the long shadows. Besides, we have Saturday off and can rest up for the profit of the night. Pity those who have to work.

In his kitchen at the Watergate, chef Jean Louis Palladin cooks for five hours straight, one eye on his customers, one finger testing the sauce.

Saturday night is a Walpurgis. It will not be ignored. Proof is in the emptiness that accompanies exclusion. In a motel, a brave business traveler tries to resist. He studies his appointments list for Monday; he totals his contracts signed; he itemizes his expense account. He calls the wife and kids (no answer; they're out). He lies on the bed. Soon the motel room walls begin to contract, pressing toward him, and a supernatural itching penetrates his feet. Outside lies the city, beckoning. With a cry of abandonment he springs into his shoes, leaps for his rented car, zooms toward destiny.

In his Capitol Hill townhouse, a divorced father puts his daughter to bed. This is his weekend of custody, and the next his former wife's. So a child's world unfolds in alternating Saturday nights.

Yes, the night can be quiet. Or so we hope, for we commend it into the hands of innocent baby sitters.Later, as we take them home, money in hand, the transparent faces of these girls give no hint of the terrors of their sentinelship. Perhaps we say, guiltily, "Did Randy throw up much?" just as we release them toward their lighted porches. Or, "Ha ha-were there any strange sounds from the attic this time, dear?"

Leslie Ruley, 14, climbs the darkened stairs of an unfamiliar house in Bethesda, thinking of all the horror movies she has seen. She looks into the bed of her 4-year-old charge and sucks in her breath. The bed is . . . empty.

It is a scientific trugh -- Einstein undoubtedly noticed it -- that as we get older, the time between Saturday nights diminishes. For a child, the week is endless, and the day off seems never to come. But for us, the pace of Saturdays speeds up, Saturday night after Saturday night, until they tick by as if on a digital counter marking off our lives.

It's Saturday night -- do we know where we are?