A time interval is the length of time which occurs between the beginning and ending of one event, or which separates two successive events.
The interval of time which occurs from the beginning to the ending of a single event is equal to the duration of the changing state or states of that event.
The interval of time which occurs from Midnight, Sunday to Noon, Monday is exactly 12 hours. Midnight, Sunday and Noon, Monday are separated by a 12-hour time interval.
The time interval which separates two successive events corresponds to the time length of the changing state or states which occurs between the events.
Two events which occur an hour apart, are separated by a time interval of one hour.
The Tuesday scowls, the Wednesday growls, the Thursday curses, the Friday howls, the Saturday snores, the Sunday yawns, the Monday morns, the Monday morns.
– Samuel Beckett