Deadline Backward Planner

A 7:00 PM deadline means starting by 5:45 PM

Say you need to be at a dinner by 7:00 PM. Getting ready takes 30 minutes, the drive takes 25, parking and walking in takes 10, and you want 10 spare minutes before the clock hits seven. Add those up and you get 1 hour 15 minutes. Subtract that from 7:00 PM and the answer is 5:45 PM. You start getting ready at 5:45, leave the house at 6:15, pull in at 6:40, walk in at 6:50, and the last 10 minutes are your cushion.

The calculator does this for any number of steps. The big time at the top is the latest moment to start. The bar under it splits the stretch from start to deadline into one block per step. The time on the left of each line in the schedule is when that step begins, so the time next to “Drive” is when you need to walk out the door. The “Based on now” box compares your clock with the plan: how long until you must start, or, if you are already behind, how many minutes you have to cut.

When it helps to plan backward

With one task, you can keep it in your head. When several things are lined up, such as getting ready, driving, parking and checking in, adding forward from the start makes it easy to forget the last step or count the cushion twice. Subtracting from the deadline begins with the question “when must the last thing be done?”, so a missing step stands out.

• Dinners, flights and work start times: the arrival time is fixed and only your prep and travel can move. The work example below shows that a 9:00 AM start with a shower, breakfast and a 40-minute commute means getting up and going by 7:25 AM.
• Exams and interviews with a check-in time: steps you rarely have, such as finding the right room, slip in. The exam example works back from 8:30 AM to a 6:10 AM start.
• Online submissions due late at night: add a final read-through, exporting a PDF and the upload, and an 11:59 PM deadline turns into 9:49 PM.
• Store or clinic cutoffs: treat the closing or check-in cutoff as the deadline, and list packing, driving and waiting in line as steps.

There is research suggesting the direction of planning matters. Park, Lu and Hedgcock (2017) compared people who planned the steps to a goal in time order with people who planned backward from the end. The backward planners felt more motivated, expected to reach the goal more, felt less time pressure and performed better on the goal. The authors explain that planning backward makes the things you need to do come to mind more clearly, and the effect was stronger for goals with complicated plans.

How the calculation works

1. Pick the deadline date and time. This is the moment you must be there, checked in or submitted.
2. Subtract the buffer from the deadline. The buffer goes in once, after the last step. 7:00 PM − 10 minutes = 6:50 PM is when the last step must end.
3. Subtract each step, starting with the last one. 6:50 PM − 10 minutes of parking and walking = 6:40 PM, minus the 25-minute drive = 6:15 PM, minus 30 minutes of getting ready = 5:45 PM.
4. The start of the first step is the answer. The schedule then shows those times again in the order you actually do things.

Latest start = deadline − buffer − (step 1 + step 2 + … + step n)

If you reorder steps and the total stays the same, the first step still starts at the same time. What changes is when each step begins, so if one of them matters, like the time you leave the house, keep the order true to life. The up and down arrows on each line reorder the steps and the times update right away.

Examples for everyday situations

These are the same examples as the buttons above the planner. “Try it” puts one into the planner without reloading the page, and the date is set to the nearest day whose start time has not passed yet.

The minutes are typical guesses. If you have your own records, use those instead. Driving and transit times swing a lot with weather and time of day, so check a maps app with your departure time set before you rely on a number.

How much buffer to leave

A buffer absorbs the step that runs longer than expected. People tend to guess too short. Buehler, Griffin and Ross (1994) ran five studies with 465 college students and found that people were overly optimistic about when they would finish academic and everyday tasks. When predicting, they focused on a future scenario and did not think much about how long similar tasks had taken before. When people were told to connect relevant past experience to their prediction, the optimistic bias disappeared. This pattern is called the planning fallacy.

For travel time, the US Federal Highway Administration (FHWA) uses a buffer index that you can borrow. It is the gap between the average trip and a near-worst-day trip (the 95th percentile), divided by the average. In the FHWA example, an average trip of 20 minutes with a buffer index of 40% adds 20 × 40% = 8 minutes, so you plan for 28 minutes to arrive on time on most days.

The buffer index differs by road and by time of day. The 20, 40 and 60% rows are for comparison. The most realistic number is how many minutes longer your slowest recent trip on that route took than usual, and that is what to put in the buffer field.

Reading the “Based on now” result

The “Based on now” box assumes you have not started any step yet and compares the current time (to the minute) with the calculation. For the dinner example (start 5:45 PM, steps adding up to 1 hour 5 minutes, 10-minute buffer) it reads like this.

When the current time falls between the start and the deadline, a “Now” needle appears on the bar, blocks that are already behind you fade, and the step you should be on according to the plan gets an outline. In the schedule, the dot on that step blinks. If you are already moving along the plan, that marker tells you more than the sentence does.

Plans that cross midnight, and the 12:00 AM problem

When the deadline is in the early morning, the start slips to the day before. With a 12:20 AM deadline on October 25 and the same 1 hour 30 minutes of work, you start at 10:50 PM on October 24. Any step on a different day than the deadline gets the date under its time, so you do not mistake it for the same day. The same goes across New Year: a 12:15 AM deadline on January 1 minus 30 minutes is 11:45 PM on December 31.

On a 12-hour clock, 12:00 AM is midnight and 12:00 PM is noon, and people mix them up often. A deadline of “12:00 AM on the 23rd” is the start of the 23rd, which is the night of the 22nd. Enter the 23rd with 12:00 AM and you get a plan that ends on the night of the 22nd. “Midnight on the 23rd” can mean either night depending on who says it, so unless the notice spells out a time like 11:59 PM, ask whoever set the deadline.

Most of the US switches to daylight saving time in March and back in November. The planner subtracts real elapsed time, so on the day clocks change, the wall-clock gap between two steps can look an hour different, but each step still takes exactly the minutes you entered. The calculation follows your device’s time zone.

Common mistakes

• Subtracting the buffer twice: if your 45-minute drive already includes 10 spare minutes and you also type 15 into the buffer field, you are setting aside 25. Put the cushion in one place only.
• Counting time twice: if your maps app’s trip time already includes walking or a transfer, do not add “walk to the station” again. Add only what the map leaves out, like parking or finding your way inside a building.
• Listing overlapping tasks in sequence: if you shower while the laundry runs, entering both one after the other pushes the start earlier than needed. Enter only the longer of the overlapping tasks.
• Reading “start” as “leave”: the big time is when the first step begins. The time you leave the house is the time on the drive or travel step in the schedule.
• Not checking the date: for a 12:00 AM deadline or an early flight, the date field must be the deadline day for the start date to come out right.

Limits and cautions

• Steps are assumed to happen one after another. For tasks that overlap or that you can do while waiting, judge the total time yourself and enter that.
• Traffic and the rules at the place you are going to, such as check-in or doors-open times, are not part of the calculation. It only subtracts the minutes you enter, so check a maps app and the host’s instructions before you leave.
• Times go to the minute, there are up to 12 steps, each step is 1 to 1,440 minutes and the buffer is 0 to 1,440 minutes. Split anything longer than a day into several steps.
• The date and time are read in this device’s time zone. If the deadline is in another time zone, convert it to this device’s local time first.
• This page does not send reminders. If you need an alert, download the calendar file and open it in your phone or computer calendar. An alert is set for the start of the first step.
• Everything is calculated inside this browser and nothing you type is saved. Only when you press “Copy link” do the deadline and steps go into the address.

Sources

• 01Park, J., Lu, F.-C., & Hedgcock, W. M. (2017). Relative effects of forward and backward planning on goal pursuit. Psychological Science, 28(11), 1620–1630Backward planning raised motivation and goal expectations, lowered time pressure and improved performance, with larger effects for complex goals
• 02Buehler, R., Griffin, D., & Ross, M. (1994). Exploring the “planning fallacy”: Why people underestimate their task completion times. Journal of Personality and Social Psychology, 67(3), 366–381Five studies (465 college students): finish-time predictions were optimistic, and the bias disappeared when past experience was linked to the prediction
• 03Federal Highway Administration (FHWA): Travel Time Reliability: Making It There On Time, All The TimeBuffer index = (95th percentile travel time − average) ÷ average; a 20-minute average at 40% adds 8 minutes
• 04WHATWG HTML Standard: date and time inputs (type=date, type=time)Input values are a date with no time zone and an hour:minute string, and the displayed format can follow device settings
• 05IETF RFC 5545: Internet Calendaring and Scheduling Core Object Specification (iCalendar)Format of events (VEVENT) and alarms (VALARM) in a calendar file (.ics)

Frequently asked questions

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