5 CFR 630.303: Part-time employees; earnings.

A part-time employee for whom there has been established in advance a regular tour of duty on 1 or more days during each administrative workweek, and a part-time employee on a flexible work schedule for whom there has been established only a biweekly work requirement, earn annual leave as follows:

(a) An employee with less than 3 years of service earns 1 hour of annual leave for each 20 hours in a pay status.

(b) An employee with 3 but less than 15 years of service earns 1 hour of annual leave for each 13 hours in a pay status.

(c) An employee with 15 years or more of service earns 1 hour of annual leave for each 10 hours in a pay status.