When is a government holiday not a holiday for government workers?

The answers, if you work for the Agriculture Department's Food Safety and Inspection Service, are the next Memorial, Independence and Labor days -- paid holidays FSIS workers will lose this year.

The service, which has more than 6,000 employes, has decided to make the spending cuts required by the deficit reduction act by not paying workers on those days.

To accomplish this, workers will be placed on furlough May 26, July 4 and Sept. 1, days when none of them would be working anyhow, and when other federal employes will be enjoying a paid day off.

FSIS decided on the highly unusual holiday/furlough approach to avoid having to shut down operations on regular workdays.

That way, its clients, the nation's major meat and poultry processing plants, won't lose time or money because federal inspectors can't be on hand.

While owners and employes of the meat plants may be happy with the decision, not all Agriculture Department workers are.

A number have called to complain that the holiday furloughs seem unfair, if not illegal.

If they are going to be furloughed, they say, why not let them off on a work day rather than a holiday? Several federal unions and members of Congress are asking the same thing.

The unions are planning to challenge the Agriculture decision in court, and some members of Congress have asked for legal opinions to see if the holiday furloughs are permitted.

When we first checked on the plan several weeks ago, Office of Personnel Management officials hadn't heard about it. Several said the only way employes could be furloughed on a holiday would be if the days before and after the holiday were included.

But those officials later said they had been mistaken and that Agriculture had been given the green light to go ahead.

Meantime, some other agencies considering imposing their own furloughs during the fiscal year that ends Sept. 30 are watching the Agriculture Department situation with great interest.

So are some of their employes. Investment Plan

The National Federation of Federal Employees is offering an individual retirement account program for its members.

The no-fee IRA gives members several investment options; contributions can be made via payroll deductions. Agencies and Overtime

I incorrectly included the Department of Housing and Urban Development in yesterday's listing of agencies that spend the most on overtime pay.

HUD should have been in the listing of those that spend the least.

According to Office of Personnel Management data (for fiscal 1984) the Postal Service was the overtime king, paying out $1.9 billion, followed by Defense ($963 million), Health and Human Services, and the Tennessee Valley Authority.

Departments that spent the least for overtime -- in addition to HUD, which paid out $2.9 million in fiscal 1984 -- were Education and Labor. Meeting

Former Office of Personnel Management director Donald Devine will talk about his experiences in government at a luncheon Monday of the D.C. League of Republican Women. The meeting will be at the Capitol Hill Club. For reservations, call 296-2877.