"D-Day" is most commonly known as a military term referring to the date of a significant operation or invasion. However, there are several synonyms for this term that can be used in various contexts. For example, the term "day of reckoning" can be used to refer to a crucial date or event that determines the outcome of a situation. "Deadline" is another synonym that is commonly used to refer to a specific end date for a project or task. "Moment of truth" is a term used to describe a critical moment when a decision must be made or action taken. Other synonyms for "D-Day" include "turning point," "crucial moment," and "watershed moment".