What is the difference between activity and event ?

[shivajikobardan]

I am studying about components of a system.

Activity-:

It is What entities do to cause changes is activity. It is represented by time period of a specified length.

Event-:

Event is defined as an instantaneous occurrence that might change state of the system. Endogenous events occurs within the system and exogenous events occurs outside the system.

eg-: making a deposit is an activity, arrival of customer is an exogenous event and completion of service of a customer is an endogenous event.

I don't see any difference between them. making deposits can also be an event as it'll change the state of the system. i.e money in bank account.

The one difference that can be taken from these definitions is "instantaneous" vs "time period' but the examples don't deliver anything about it.