The District government is taking a "don't worry, be happy" attitude toward the year 2000 date change at midnight tomorrow: The city is not expecting disruptions and is prepared if there are, so officials are encouraging people to come downtown for the national and local millennium celebrations.

"We have met our goal," Mayor Anthony A. Williams (D) said of the city's 19-month, $140 million effort to check and fix all its critical computer systems. "Residents, businesses and visitors can rest assured that city services will function. We can all focus on enjoying the holidays and celebrating the millennium."

Although Washington, as the nation's capital, is on high alert for possible terrorist activity, D.C. Police Chief Charles H. Ramsey said he is not aware of a specific threat made here. He is asking people to attend parties and activities on the Mall as they had planned but to be "extra vigilant" in noticing what is going on around them.

The city began staffing its Y2K command center Tuesday and will keep it open at least until next Tuesday. The command center is where officials representing law enforcement, emergency rescue, utilities, transportation and other key services will gather to direct the District's Y2K response, if needed. All major city agencies also will have representatives there at Williams's behest.

Unless telephone service is disrupted, residents should be able to call 911 for emergencies or the police non-emergency number, 202-727-1010. Bell Atlantic Corp. officials have told the District they are satisfied with the city's tests of the 911 system.

"I am confident that people with a true emergency on January 1 will be able to pick up the phone and reach a 911 operator," Ramsey said.

Fearing an overload of 911 calls from people just checking to see if it works, Ramsey urged residents to call 911 only in an emergency.

If telephone service is cut off--and officials don't expect that will happen--residents would be able to report problems to 125 "emergency service sites" across the city where authorities will have mobile radios. The locations include firehouses, community centers and businesses. A map of the sites accompanies this story.

Authorities also have identified 150 "critical" intersections at which police officers would help direct traffic if the lights went out.

Eighteen months ago, a question arose about whether the city would make the computer fixes in time. None of the computers had been checked, much less repaired. The underfunded emergency preparedness office had few supplies. The District was featured in news reports--including the CBS-TV "60 Minutes" program--as one of the nation's worst-prepared big cities.

"We knew that we would run hard to the end," said Suzanne Peck, who was brought in in July 1998 to lead the Y2K conversion effort. It involved checking, repairing or replacing and testing hundreds of applications and pieces of equipment so the computers would not read the year 2000 as 1900.

All 378 of the city's critical computer systems have been debugged and tested, Peck said, and more than 3,300 Y2K-ready desktop computers have been installed in the agencies that provide essential services.

The mayor noted that a side benefit of the effort is that the city's antiquated computer technology has been upgraded in addition to its preparations for emergencies. In addition to Peck, the city hired a new emergency preparedness chief who quickly rebuilt that agency.

"Y2K was a crisis turned into an opportunity," Williams said.

What follows is a capsule of major agencies' preparedness and backup plans:

* Consumer and Regulatory Affairs: The agency has preprinted licensing records for corporations, businesses, alcoholic beverage control and occupational and professional licensing applications and renewals. Director Lloyd J. Jordan said the agency could shift to a completely manual system if there are technological troubles.

* Courts: Unlike the rest of the late-starting city, courts in the District began Y2K preparations about three years ago and finished in August. Much of the computer hardware and software used by the Court of Appeals and Superior Court to track and manage cases have been replaced. Residents with court-related matters should expect no disruptions.

* Employment Services: The U.S. Department of Labor is aiding the city's labor agency in making sure unemployment benefit checks are distributed without delay. Worker's compensation and disability compensation checks are not expected to have glitches either.

* Fire and Emergency Medical Services: Interim Fire Chief Thomas N. Tippett said the city's critical systems needed for firefighting and rescue have been checked, upgraded and tested to comply with the date change. He urges residents who don't have 911 emergencies to call 202-462-1762 to request services.

* Health and Hospitals: Medical and computer equipment at D.C. hospitals and community health centers has been checked, repaired or replaced for the date rollover. If there are problems with utilities, health officials have contingency plans including stockpiles of drinking water and drugs.

* Human Services: Welfare benefit checks have been processed through January as a precaution, but a manual processing system also is in place. Food stamp recipients use electronic benefit transfer cards (EBT) to access benefits. If those systems fail, benefits may be obtained at two training sites.

* Personnel: City employee payroll and retirement checks, including direct deposit, will be issued as usual next month. Deductions for health insurance and retirement or other programs will be transmitted to the insurance carrier and financial institution on time. Checks have been printed in advance in care of problems and would be distributed at each work location.

* Police: One of the city agencies whose computer technology was upgraded substantially, the police have faster, more reliable systems providing officers with information on criminal histories, wanted and missing persons, vehicles and driver's permits, firearms and other data.

* Public Works: "Our primary concern is having electricity," said Public Works Director Vanessa Dale Burns. "Should there be a disruption of power to our traffic signal system, the 1,400 individual traffic-control boxes will continue working. If any of these boxes lose power, the signals will flash red, which is a signal to motorists and pedestrians to stop and proceed cautiously."

* Schools: The last repairs to security and fire alarm systems were made in October, part of an effort by the schools to check and fix more than 15,000 pieces of equipment in 155 buildings. But just in case, officials extended the winter break a few extra days, to Jan. 6.

* Water and Sewer Authority: Backup generators are in place at the authority's Bryant Street water-pumping stations in case they are needed to ensure delivery of drinking water.