In Scrum there are iterations or cycles of up to one month called Sprints. A completed sprint should always produce something of tangible value for the customer or user
For all sprints there is a time frame (Timebox) with a fixed start and completion time, which should be the same for all sprints. The completion of a previous sprint is immediately followed by a new sprint.
Even if there are changes to the scope of services or personnel that would affect the target and therefore should not actually be made during a sprint, this is sometimes unavoidable due to certain business needs.