Which prefix signifies "before" when referring to time?

The prefix that signifies "before" when referring to time is ante-. This prefix originates from Latin, where it means "before" or "in front of." In the context of time, "ante" is used to indicate an occurrence that happens prior to a specific point or event, such as in "antebellum," which refers to the period before the war, specifically the American Civil War.

In contrast, post- means "after" or "following," and is used to describe events that occur later in time relative to a specified reference point. Pro- is a prefix that can mean "for" or "in favor of" and does not specifically refer to time. Lastly, dia- typically indicates "through" or "across" or can relate to a day, but does not denote a temporal relationship of being "before." Thus, ante- is clearly the prefix that conveys the concept of "before" in temporal discussions.