5 U.S.C. § 6327

1. (a)An employee in or under an Executive agency is entitled to leave without loss of or reduction in pay, leave to which otherwise entitled, credit for time or service, or performance or efficiency rating, for the time necessary to permit such employee to serve as a bone-marrow or organ donor.
2. (b)An employee may, in any calendar year, use—
   1. (1)not to exceed 7 days of leave under this section to serve as a bone-marrow donor; and
   2. (2)not to exceed 30 days of leave under this section to serve as an organ donor.
3. (c)The Office of Personnel Management may prescribe regulations for the administration of this section.