Official Time Reform Act of 2017 This bill prohibits the granting of official time to an employee who would otherwise be in a duty status for purposes of engaging in any political activity, including lobbying activity. Official time is time off from assigned duties granted to a federal employee for purposes of representing a union or its bargaining unit employees. Under the Civil Service Retirement System and the Federal Employees Retirement System: (1) an employee may not be allowed retirement credit for any day of service spent principally on official time that is in excess of 365 days in the aggregate, (2) an employee is deemed to have spent a day principally on official time if it is at least 80% of the time such employee would otherwise be in a duty status, and (3) any such service spent principally on official time for which an employee is not allowed credit shall be treated as credible service for purposes of calculating the employee's average pay.