What is a leave-by alert?
A leave-by alert is a real-time departure notification that factors current Apple Maps traffic, the event’s location, and any travel buffer into a single “time to leave now” moment. The term “leave-by alert” is used by Composed for this specific calculation; the generic industry phrase is “drive-time alert,” but most drive-time alerts ignore current traffic and skip flight buffers entirely.
How does a leave-by alert work?
A leave-by alert resolves the event’s coordinates, queries Apple Maps for the current travel time from your present location, adds a buffer appropriate to the event type, and schedules a local notification for the resulting departure timestamp. In Composed, flights get a 120-minute domestic or 180-minute international airport buffer added on top of drive time; non-flight events get a small parking-and-arrival buffer. The alert recalculates if traffic changes within eight hours of the event.
What’s the difference between a leave-by alert and a regular reminder?
A regular reminder fires a fixed number of minutes before the event — fifteen minutes, an hour, a day. It doesn’t know the traffic, the distance, or whether you need to clear airport security. A leave-by alert works backwards from arrival: how long the drive will take right now, plus how much margin you need on the other end. The result is one alert at the actual decision moment, not a stack of arbitrary pings.
Why does the term “leave-by alert” exist?
Most calendar apps describe departure as “drive time” or “travel time,” which frames the alert as a passive estimate. “Leave by” frames it as an instruction at the moment of action. The shift matters for users with time blindness or executive-function fatigue: an instruction that says “leave now” is acted on more often than an estimate that says “your commute is 25 minutes.”
Get Composed
Composed builds the leave-by alert into every event with a place. Download Composed on the App Store and try it free.
Related: voice-to-calendar · three-layer reminders · calm planning · calendar prep tasks