21 years

Twenty-one years is a significant period, roughly equivalent to a little over two decades. During this time, a person can experience many life events, such as completing education, building a career, forming relationships, and experiencing personal growth. It's enough time for substantial change and development, both individually and globally. In historical terms, many social and technological advancements can occur within this span, shaping society's landscape. Essentially, 21 years is a meaningful span that can mark major milestones in personal or collective journeys, reflecting growth, change, and continued progress over time.