In August, my parents will be married for twenty-five years. What is the correct phrasing for this sentence?

The correct phrasing is "will have been married for twenty-five years" because it accurately reflects the future perfect continuous tense. This tense is used to indicate that by a specific future point in time—in this case, August—an action will have been completed for a certain duration. Here, the marriage has been ongoing for twenty-five years by that point, so using "will have been" effectively conveys that the duration of the marriage will be completed at that time.

The choice emphasizes not just the duration but also places it squarely in the future, making it clear that it refers to a milestone that will be reached. This tense usually involves a time reference that specifies when the action will be considered complete, which serves to clarify that the anniversary occurs in August.