Every event that can occupy a span of time can also warp how long that duration feels. No shortage of factors configures such duration estimates, yet they remain largely confined to events experienced in the present moment. Might future events similarly impact duration? The present investigation leverages a phenomenological return trip effect, which documents subjectively longer outbound journeys relative to identical inbound journeys, to inform this question. Through this lens, the focal event (that which will transpire at the destination) can be decoupled from the focal duration (the span of time between the present moment and arrival at that destination). Four studies document a consistent effect in which ambiguity awaiting at a future event (occurring at the destination) expands the subjective magnitude of present durations (the travel time to the destination). Duration judgments thus appear sensitive to an increasingly broad scope of factors, informing models of temporal cognition.