Civilian Personnel Office extends hours of operation Published May 4, 2017 By 28th Force Support Squadron ELLSWORTH AIR FORCE BASE, S.D. -- The Civilian Personnel Office extended their hours of operation to better serve customers. Current hours are now 7:30 a.m. to 4:30 p.m., Monday through Friday, with the exception of federal holidays. For additional information, please call CPO at (605) 385-2474.