Like many other federal employment cases in which paid leave time is at stake, it boiled down to a definition: whether 15 days of leave for military training should be measured in calendar days or workdays.

For decades, the government said the "15 days" of paid military reserve training guaranteed in law for federal employees were calendar days. Under that practice, most federal employees were charged leave according to the time they were away for National Guard and reserve training rather than the number of workdays missed at their agencies. As a result, the employees were charged military leave for weekends and holidays when they were not scheduled to work at their civilian government jobs.

But a federal appeals court, in a case called Butterbaugh, ruled that the government was wrong to measure by calendar days and that federal employees in the Guard and reserves should not be charged for leave for "non-workdays" when they were away for military service.

"As a general matter, employees are not accountable to their employers for time they are not required to work," the U.S. Court of Appeals for the Federal Circuit said. "We see no reason why federal employees need military leave for days on which they are not scheduled to work."

After the ruling in 2003, federal employees started filing claims to recover lost leave. Many of the employees believe that they are owed money because they sometimes had to use regular vacation time if their military duties required more than the 15 days.

Bush administration officials say they do not know how many employees were shortchanged. But the number may be in the thousands, and the cost to agencies and taxpayers could be substantial.

A new round of Butterbaugh litigation deals with the question of how far back employees can go to reclaim leave. It may take the government six months or so to resolve that issue, some officials say.

Like many employment cases, Butterbaugh has a twist or two. For example, Congress in 2000 amended the law on military leave, making it clear that federal employees were not to be charged for weekends while away for reserve training. The Office of Personnel Management sent a memo to agencies advising them to change leave policies to conform to the new guidelines.

That means that most claims under Butterbaugh involve past and not current agency policies.

It's also important to note that OPM has not issued regulations in this area. Instead, it has shaped its guidelines for agencies based on court cases and rulings from the comptroller general. OPM says it found no authority in law to justify a regulatory approach, a development that limited scrutiny of leave calculations over the decades.

Because Butterbaugh covers military leave cases before 2000, when the law was amended, the statute of limitations has become an issue. OPM uses the standard six-year limit for the filing of administrative claims through agencies. That means claims are now being accepted from 1999 only, and the window is closing fairly quickly.

Federal employees who were shortchanged on leave also can bypass their agencies and file claims directly with the Merit Systems Protection Board. The board has signaled that it does not believe the six-year statute of limitations applies under the Uniformed Services Employment and Reemployment Rights Act. That means eligible employees can file USERRA claims going back to Oct. 13, 1994, the date of the law's enactment.

The MSPB has sent the first of several USERRA cases back to an administrative judge, opening the door for the judge to review past laws and figure out whether any laws before 1994 might provide relief.

The judge's decision probably will influence how MSPB handles subsequent appeals.

OPM officials are watching the proceedings at MSPB. They can appeal the MSPB's decision if they think it is in error or harmful to the civil service. For the short term, they plan to continue processing leave cases as called for under the 2000 statutory change.

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