“Base period” means the first four (4) of the last five (5) completed calendar quarters immediately preceding the first day of an individual's benefit year; provided, that if the first quarter of the last five (5) completed calendar quarters was included in the base period applicable to any individual's previous benefit year, the individual's base period shall be the last four (4) completed calendar quarters. For the purposes of establishing a base period in cases involving persons receiving workers' compensation benefits for temporary total disability, the department shall exclude periods of such disability from the base period and determine the base period from the last four (4) completed quarters of work before any such disability.