It was a kind of miniholiday within a holiday season, a gift of time in a time-hungry city. And brief and fleeting though it was, Washingtonians required only minimal prodding to discuss the values and drawbacks of the extra second added to yesterday's normal quota of 86,400.

"I'll welcome that extra second," said Prince George's County Council member Sue V. Mills, who said she would use it to plan her political future.

"Everybody's been guessing," she said. "Maybe after that second they won't have to guess."

"With that extra second," said Alexandria Mayor James P. Moran Jr., who was planning to stay home with his two children Jimmy and Mary, "I'll try to snuggle closer to them and try to make up for all the evenings I've had to be out at meetings."

A man with a professional interest in time, Michael Bray, of the wage and hour unit of the D.C. Department of Employment Services, said he would defer immediate recognition of the extra instant to "add it on in the middle of tomorrow and take an extra second of skiing" at Roundtop in Pennsylvania.

Sarah Ray, wife of D.C. Council member John Ray (D-At Large), said she was sure the extra second would be put to good use in helping her three children with their ABCs.

While there may not be a one-second moratorium on growth in the national debt in the strictest sense, according to a spokesman for the Treasury Department bureau that deals with that infamous fiscal burden, "If you wanted to stretch, you could say you have a free second."

The smallest unit of time used in calculating what the nation owes, it turns out, is not the second, or even the minute or the hour, but the day, according to Bureau of Public Debt spokesman David Liebschutz.

So "in reality, this extra second does not add {to} or subtract {from} the debt," he said.

On the other hand, Americans aren't likely to get that extra second's worth of interest on their savings bonds, either.

"Since the interest rate is calculated semiannually, I don't know that it {the extra second} would affect it at all," said bonds spokesman Jim Gianfagna.

Nor was the extra second, which was inserted to keep clocks synchronized with the slowed rotation of the earth, expected to be of value to inmates of the District's penal institutions, who are counting the moments until the end of their sentences.

"We don't go by the second," in computing length of terms, said Edward D. Sargent, a spokesman for the Corrections Department. Sentences, he said, are based on days, and irrespective of the number of seconds in each, "one day fits all."

Announcement of the addition of the extra second, inserted in the normal flow of time last night just a second before 7 p.m., came too late for Metro to warn its passengers, or adjust timetables.

But "we have this tremendous respect for Washingtonians," said Metro spokeswoman Beverly Silverberg. "We know they will be able to cope with this extra second."

One night this month, the District's main post office canceled 1.5 million pieces of mail, and an extra second might have come in handy. But last night, said Tour Superintendent Charles Hill, the eight cancelling machines were expected to finish by 9:15 p.m. with all stamped mail picked up in town. "That extra second won't help us tonight."

The Potomac Electric Power Co., on the other hand, expects to consume an extra 400 pounds of coal in generating additional electricity to meet the demands of the extra second, said spokesman Tom Welle.

Bill O' Connell, an Army major in the Pentagon, said he planned to "use that second to reflect on all the good things that happened in 1987 and be thankful that I'm an American citizen."

Audrey Moore, who waged a vigorous campaign to win election as chairman of the Fairfax County board of supervisors, said she was "probably going to get one extra second of sleep . . . just rest."