More than 40,000 federal employes in six outlying counties here will have to work on Inauguration Day, even though that day is a holiday for their 300,000 colleagues closer to downtown.

Monday, Jan. 21, is a special holiday for most federal workers in the Washington area. Postal employes are the exception, and will have to work.

But Washington feds who are out of town on official business on the 21st will have to work, while out-of-town feds who are on duty here that day will get a bonus holiday. If you are confused, welcome to the club.

Because the holiday is limited to federal employes working in the close-in metropolitan area, there will be many questions about who does what to whom, and for how long, on the 21st.

The special holiday, designed to clear city streets and government buildings for the inaugural parade. is limited to the District, to Montgomery, Prince George's, Arlington and Fairfax counties, and to the cities of Alexandria and Falls Church. Feds who work in those areas, regardless of where they live, get the day off.

But workers whose offices are in Maryland's Charles, Calvert and Frederick counties, or in Virginia's Loudoun, Prince William and Stafford counties or in the Virginia cities of Fairfax, Manassas and Manassas Park will have to report for duty even if they live in the holiday zone.

Those areas officially became part of greater Washington last year, but they don't qualify for the holiday because they were not in the metropolitan area when the Inauguration Day law was drawn up 20 years ago.

Workers who commute from outside the holiday zone to offices inside the zone will get the day off. That will affect many feds who live in West Virginia, Pennsylvania, Western Maryland, the Eastern Shore and outlying areas of Virginia but who work in the District or adjoining Maryland and Virginia counties. They will be off on the 21st even though their hometown federal offices will be open for business.

Just the opposite will apply to feds who live in the District, Montgomery, Prince George's and Northern Virginia if they work in an office outside the holiday zone.

The geographic quirk of the holiday will mean problems for agencies that are bringing out-of-town workers here that week for training. In most cases, the first day of training will be dropped because the employes have come into the holiday zone.

By the same token, feds based in Washington -- who normally would get that Monday off -- will have to work as usual if they are on assignment elsewhere.