who created the stages of adult development like for example the trying 30's?

Gail Sheehy wrote 'Passages' (1976), which described predictable stages of adult development including 'The Trying 30s.' Her work identified passages or transitions that adults go through approximately every decade, challenging the idea that development stops at adolescence. She popularized the idea of developmental crises in adulthood, influencing how people think about adult life stages.