OnTime
A time assistant that turns calendar events into reverse timelines, so you know when to prepare, leave, and arrive.
product siteCalendars tell you when an event starts.
They do not tell you what needs to happen before then.
OnTime started from that gap. If a meeting starts at 9:00, the useful question is not just what time it is. It is when to wrap up, get ready, and head out.
I built OnTime as a personal time assistant for iPhone. It turns each calendar event into a reverse timeline:
wrap up → get ready → leave → arrive
Instead of one distant deadline, the app shows one next step at a time.
The calendar is the starting point
OnTime reads the events you allow and builds timelines for the next part of your day. Calendar data is processed locally, so the information behind personal plans stays on the phone.
The timeline can account for:
- event start time
- getting-ready time
- transition and early-arrival buffers
- travel time from MapKit
- location and route changes
The output is deliberately simple. On the home screen, the question is: what should I do now?
From departure math to a timeline
The core engine works backward from the event:
Event → arrive → leave → prepare → transition
This makes time visible before it becomes urgent. If travel takes longer, the leave window shifts. If an event is approaching, the current step becomes more immediate. If there is nothing ahead, the home screen can stay quiet with “all clear”.
Planning the steps
Not every event needs the same preparation.
Plan Your Steps lets an event carry a getting-ready checklist. These checklists became reusable time recipes, so the same sequence can be attached to future events, scheduled, shared, or started as a focus session.
The app can move from a general prep duration to a more specific sequence:
write recipe → attach to event → follow each step
That made the planning model useful for more than travel. It became a way to make invisible preparation concrete.
Native when it matters
OnTime is built around the parts of iPhone that are useful when time is already moving:
- EventKit for calendar events
- MapKit for travel-time estimates
- local notifications for timeline steps
- Live Activities and Dynamic Island for the current action
- widgets for upcoming timelines and recipe progress
- haptics and focus sessions for moments that need attention
The app does not need to keep showing the whole plan. It can put the next useful instruction where it is easiest to see.
A calmer interaction model
The goal is not to promise perfect arrival times.
Travel estimates can change. Calendar events can move. People can take longer to get ready.
The product is designed around that reality. Buffers are controllable, late states are explicit, and the interface uses action-oriented language such as “Time to get ready” and “Head out now”.
This keeps the experience practical. It gives you a next step without pretending the day is perfectly predictable.
What I learned
A calendar is good at recording commitments. It is not good at explaining the work required to reach them.
The interesting product decision was to turn each event into a sequence of actions, then surface only the step that matters now.
OnTime started in March 2026 as a reverse-timeline experiment. It grew into a native system for planning, reminders, recipes, focus mode, and lock-screen awareness.
The simple loop became:
Calendar event → reverse timeline → next action → arrive