Unions usually have the final say on how the furloughs will be implemented, said Colleen M. Kelley, president of the National Treasury Employees Union (NTEU). She said they get to bargain with federal agencies on issues such as how the furloughed days will be spread out.

The exact number of total furloughs planned is still unavailable, since agencies are still deciding how to spread the cuts. It's possible some agencies may yet be able to spare some employees from furloughs or at least minimize days of unpaid leave.