From WP's article on state of affairs:
In philosophy, a state of affairs (German: Sachverhalt), also known as a situation, is a way the actual world must be in order to make some given proposition about the actual world true; in other words, a state of affairs is a truth-maker, whereas a proposition is a truth-bearer. Whereas states of affairs either obtain or fail-to-obtain, propositions are either true or false. Some philosophers understand the term "states of affairs" in a more restricted sense as a synonym for "fact". In this sense, there are no states of affairs that do not obtain.
This term may be seen as a scientifically realistic metaphysical claim about the world. That there is an external world, that things there are objectively knowable things and events, and the term is often used in terms of an understanding of truth that is correspondent. From WP:
In metaphysics and philosophy of language, the correspondence theory of truth states that the truth or falsity of a statement is determined only by how it relates to the world and whether it accurately describes (i.e., corresponds with) that world... Correspondence theories claim that true beliefs and true statements correspond to the actual state of affairs. This type of theory attempts to posit a relationship between thoughts or statements on one hand, and things or facts on the other.
Now, what is relevant in the state of affairs is contextual or normative to the observation which means there's no hard and fast rule as to what applies in any given situation, particularly if you're talking about an event. From WP:
In philosophy, events are objects in time or instantiations of properties in objects. On some views, only changes in the form of acquiring or losing a property can constitute events, like the lawn's becoming dry. According to others, there are also events that involve nothing but the retaining of a property, e.g. the lawn's staying wet. Events are usually defined as particulars that, unlike universals, cannot repeat at different times. Processes are complex events constituted by a sequence of events. But even simple events can be conceived as complex entities involving an object, a time and the property exemplified by the object at this time. Traditionally, metaphysicians tended to emphasize static being over dynamic events. This tendency has been opposed by so-called process philosophy or process ontology, which ascribes ontological primacy to events and processes.
So, what should we take from these definitions of event? "On some views" hints at there's no hard and fast rule, sorry. It's whatever the discussion decides is observable or relevant. In fact, this aspect came back to bite the logical positivists in the butt in their quest for the "objective observation" in the form of theory-ladenness, which basically maintains that part of what you observe in the state of affairs is constrained by your theoretical prejudices.
Thus, in philosophical discourse, what counts as an event in regards to the state of affairs is afforded a certain principle of charity, which is sort of an intuitional approach to playing the language game fairly. Another philosophical term to describe this willingness to decide what an event is by consensus in the dialog is called cooperative principle in the philosophy of language. In this way, the nature of the event is constrained by shared intentionality. (Of course, in an argumentative epistemological process, such as trial law, the parties may agree to disagree with both the prosecution and defense trying to persuade the judge what the event is!)
Why is this necessary? It's possible to argue that any event is really an infinite number of objects, sub-events, caused by an infinite number of causes and so on, and philosophical dickering usually manifests itself as a difference in metaphysical presuppositions. That is to say, there's a certain politics involved when two parties are engaged in elenchus.
