What time do I need to leave?

How this works

It starts at the time you have to be there and walks back. Take off the minutes to park and find the room: that’s when you arrive. Take off the trip: that’s when you leave. Take off getting ready: that’s when you start. Those last two are the times you count down to. The start of the appointment is shown, but it’s the one number the plan doesn’t need you to watch.

Each of the two gets a heads-up beforehand. An alert at 9:25 for a 9:25 leave is already too late, because there’s no time left to find your keys; the early one is the one that helps. If getting ready is shorter than the heads-up, the “start getting ready” alert is already your warning before leaving, so the page doesn’t add a second one on top of it.

With the defaults filled in, it reproduces the worked example from our guide to dealing with time blindness: appointment at 10, a 25-minute drive, 10 minutes to park and find the room, so leave at 9:25, so start getting ready at 9:00.

Where the numbers come from

The method is fixes 3 to 6 of the time blindness guide: plan backwards from the time you have to leave, add half again to any estimate (a 20-minute task gets 30), plan with numbers you’ve timed rather than ones you feel, and give every switch a heads-up 5 to 15 minutes before it. The guide’s starting routine uses 10, which is the default here.

Three things are ours, and worth knowing which. Guesses round up to the next 5 minutes. The half again stops adding at 30 minutes per number, because half again of a three-hour guess is an hour and a half of waiting, and a long trip is the easiest guess to replace with a real number. And trips over four hours, or getting ready over three, get a different answer instead of a plan: those have a departure someone else set, or are blocks of their own.

If you’re not sure, call it a guess

Timed numbers go in as they are. If you haven’t actually timed one, choose a guess and let it get the buffer. Arriving ten minutes early costs ten minutes. Arriving ten minutes late usually costs more, and with time blindness the felt number is the one that runs short: the guide’s point is that real numbers are almost always longer than guesses, sometimes by double. The better fix is to time the trip and the getting ready once, then come back and choose “All of them”.

Frequently asked questions

How do I work out what time I need to leave?

Plan backwards from the time you have to be there. Take off the time to park and find the room, then the trip: that is when you leave. Take off how long getting ready takes: that is when you start. For an appointment at 10 with a 25-minute drive and 10 minutes to park, you leave at 9:25 and start getting ready at 9:00. Then count down to 9:00 and 9:25, not to 10:00.

How much buffer time should I add?

A simple rule many people use is to add half again to any estimate, so a 20-minute task gets 30. A number you have actually timed can go in as it is. Real numbers are almost always longer than guesses, sometimes by double, so timing the things you do every week is the better fix than a bigger buffer.

Why count down to the leave time instead of the appointment?

Because the appointment time hides the time that matters. By the time a countdown to 10:00 looks urgent, the moment to start getting ready has already gone. Counting down to the start and the leave time puts the warning where the switch actually is, and a heads-up 5 to 15 minutes before each one gives you time to wrap up what you are doing.

Is the leave time calculator free, and is anything stored?

It is free, there is no sign-up, and nothing you type leaves your browser. If you choose Today, it reads your device clock to check whether the plan has already started; that also stays on your device.