active career; working life; playing days
Refers to the period when someone was actively working, especially before retirement, or for athletes, their playing career. Often used in retrospect.
During his working life, my father worked as a teacher.
The records from his playing days still haven't been broken.
現役 means 'active duty' or 'currently working', while 現役時代 specifically refers to the period of one's active career.
Compound of 現役 (active duty/working) and 時代 (era/period).