Complex sentence: During that time, Obama Sr. completed his undergraduate degree in economics in Hawaii in June 1962, then left to attend graduate school on a scholarship at Harvard University, where he earned an M.A. in economics.
Split into simpler sentences: During that time, the elder Obama completed his undergraduate degree in economics in Hawaii, graduating in June 1962. He then left to attend graduate school on a scholarship at Harvard University, where he earned an M.A. in economics.