Within bronfenbrenner's bioecological approach, which system underlies each of his system levels and involves the way the passage of time, including historical events, affects children's development?

Chronosystem.

Urie Bronfenbrenner, an American psychologist, developed the Ecological Systems Theory as an explanation to how children interact with their environment and how in turn the environment affects the child’s development.

The first four levels of the system are:

Microsystem (Immediate Environment)

Mesosystem (Connections)

Exosystem (Indirect Environment)

Macrosystem (Social and Cultural Values)

The last system, which underlies all the other levels is the Chronosystem. This system introduces time to the theory. It includes changes over time in a small level (changes to family structure, changes in social circle) and changes at a social level (wars, recessions, etc.).