If you're the type who plans ahead, you already know that Christmas falls on a Tuesday. A lot of people have noticed.

Half a dozen federal workers and a couple of private-sector types have called asking if the Tuesday Christmas holiday means they will get the day off on Monday, Dec. 24. That is a serious issue here.

Many local private firms, union headquarters and law offices follow Uncle Sam's lead on holidays. Department store owners (but not necessarily department store employees) delight in the prospect of 360,000 government employees let loose for an extra day during the busiest shopping period of the year. Metro and traffic officials need to know if there is going to be a break in the normal government work pattern and rush hours.

And, in the best tradition of official Washington candor, the correct answer to the bonus holiday question is: Maybe yes, maybe no!

The good news is that in 1986, when Christmas day was Thursday, President Reagan announced -- on Dec. 10 -- that nonessential government workers would get a bonus day off on Friday, Dec. 26.

The White House was careful not to call the extra time off a holiday because that would have meant paying millions of dollars to people who had to work. Instead it was an administrative day off, meaning most essential personnel didn't get an extra day of pay for working.

But before you start making plans for an extra long weekend this year, remember 1984.

In 1984, Christmas day also fell on a Tuesday. Back then, the director of the Office of Personnel Management, who prided himself in being something of a hard case, announced business as usual on Monday because of the nation's economic condition.

Anybody who wanted the day off, he said, could take vacation.

Spot checks with federal workers who survived 1984 show that many, many people took a vacation day. Others who worked recall that in many offices, both federal and private sector, not a heck of a lot of work was done that Monday.

Federal officials say it is too early to even begin guessing if President Bush will give government employees the Monday before Christmas off.

Insiders speculate that Constance B. Newman, the government's up-from-the- ranks personnel director, will encourage the White House not to repeat the Grinch act of 1984.

One thing is sure. Even if most federal workers get the day off, the U.S. Postal Service, which is a semi-independent corporation, will keep its 800,000 troops on the job that Monday.Super Health Insurance

Some of the very best health insurance plans in the federal health insurance program aren't open to most employees or retirees.

For a look at them, and the reason for their closed-door policy, check this space tomorrow.