Introspection refers to the method of analyzing emotions and thoughts of our own selves by looking inward. The word has been used in everyday conversation to report the informal process of researching one's internal life, at the same time it also refers to a more formalized process that has once been used as experimental research in psychology. This research technique can help people to make a correlation between different experiences and reactions.
The transaction actually represented revenue in the month of May. So The revenue was earned in May and thus should count towards the May accounting period.