Why Do We End Up "Just Before the Deadline"? Planning Fallacy

When starting a project, you optimistically estimate "this should take about this much time," but as the deadline approaches, you panic, "There's not enough time!" This phenomenon has a psychological name: Planning Fallacy.

What is Planning Fallacy?

A cognitive bias proposed by psychologist Daniel Kahneman and colleagues, where people optimistically believe "my tasks will go as planned" and "trouble won't happen," resulting in underestimating the time needed.

Why it happens:

Underweighting past failure experiences
Believing "this time will be different" without basis
Not anticipating unexpected troubles
Not considering conflicts with other tasks
Not accounting for fatigue or declining concentration

In other words, "poor estimation" isn't a character flaw—it's a trait of the human brain.

Reverse Planning Steps: Set Milestones by Working Backward from the Goal

To counter planning fallacy, use reverse planning: "Work backward from the deadline, divide tasks, and allocate realistic time to each stage."

Step 1: Clarify the Final Deliverable

First, define specifically "what, by when, in what state" you need to complete it.

Example: Report submission

Deadline: June 30, 2026 (Mon) 5:00 PM
Deliverable: 10 A4 pages, over 3,000 words, with cover and table of contents
Submission method: Email PDF

Step 2: Break Down the Work

Divide the process to reach the final deliverable into fine steps.

Report example:

Narrow down theme
Literature review / resource collection
Create outline
Write main text (intro, body, conclusion)
Create figures and tables
Organize reference list
Proofreading and revision
Create cover and table of contents
Convert to PDF / final check
Submit

Step 3: Estimate Time Required for Each Task

Here's the key. Estimate not "how many hours in ideal conditions" but "realistically, how many hours considering normal concentration and typical troubles."

Task	Estimated Time
Narrow theme	2 hours
Literature review / resource collection	5 hours
Create outline	2 hours
Write main text	8 hours
Create figures/tables	3 hours
Organize references	1 hour
Proofreading/revision	3 hours
Cover/contents creation	1 hour
PDF conversion/check	0.5 hours
Submit	0.5 hours
Total	26 hours

Step 4: Schedule Backward from the Deadline

If the deadline is June 30 (Mon) 5:00 PM, work backward from there.

June 30 (Mon): Submit (0.5 hours)
June 30 (Mon) morning: PDF conversion/final check (0.5 hours)
June 29 (Sun): Cover/contents creation (1 hour)
June 28 (Sat): Proofreading/revision (3 hours)
June 27 (Fri): Organize references (1 hour)
June 24–26 (Tue–Thu): Create figures/tables (3 hours)
June 17–23 (Mon–Sun): Write main text (8 hours)
June 16 (Sun): Create outline (2 hours)
June 10–15 (Mon–Sat): Literature review/resource collection (5 hours)
June 9 (Sun): Narrow theme (2 hours)

At this point, it's clear: If you don't start work on June 9, you won't make it.

Setting Buffer Time: 20% Extra is the Rule

A reverse schedule alone isn't enough. Because "unexpected troubles" and "days when things don't progress as expected" will inevitably occur.

What is a Buffer?

A buffer is reserve time—slack time. By adding "play" to the schedule, you can still meet the deadline even when trouble occurs.

Buffer Allocation Percentage

In general project management, adding 20–30% buffer to total work time is recommended.

In the report example:

Total work time: 26 hours
Buffer (20%): ~5 hours
Total required time: 31 hours

In other words, by scheduling 31 hours to complete 26 hours of work, you create breathing room.

Where to Place the Buffer

Where should buffers go? Two methods:

Method A: Distribute Across Each Task

Uniformly add 20% to each task's estimated time.

Example: Writing main text 8 hours → allocate 9.6 hours

Pros: Each task has breathing room Cons: "I have time, so I'll do it later" procrastination

Method B: Consolidate at the End

Set "reserve days" of 3–5 days after all tasks.

Example: Complete work June 9–28 → June 29–30 are reserve days

Pros: Reserve days can be used for "final checks and quality improvement" Cons: If trouble occurs mid-project, reserve days get used up

Recommendation: Hybrid of both. Add 10% to each task + 2–3 reserve days at the end.

Date & Days CalculatorCalculate the exact number of days between dates or add days to a date.

Improving Task "Estimation Accuracy" with Record-Keeping

To improve reverse schedule accuracy, it's important to know "how long each task actually takes me."

Habit of Time Tracking

Simply recording the time at task start and logging the actual time at completion dramatically improves estimation accuracy.

Recording Method Example

Task	Estimate	Actual	Variance	Notes
Literature review	5 hours	7 hours	+2 hours	Couldn't find resources, took longer
Writing main text	8 hours	6 hours	-2 hours	Was focused
Proofreading	3 hours	4 hours	+1 hour	Many typos

After recording 3–5 projects, your "estimation habits" become visible.

Example:

Literature review always takes 1.4× longer → estimate 1.5× next time
Writing goes as estimated if focused → environment setup is key
Proofreading takes longer than expected → estimate 4 hours next time

Manage with Excel or Spreadsheet

Simple table format is fine. Using Google Sheets or Notion lets you accumulate and reference past data.

Weekly Review and Schedule Adjustment Routine

A schedule isn't "set it once and forget it." Reviewing and adjusting weekly keeps your plan realistic.

How to Do a Weekly Review (15–30 minutes)

1. Review Last Week

Which tasks went as planned?
Which tasks fell behind, and why?
Did unexpected tasks arise?

2. Confirm This Week's Plan

What are this week's milestones?
Are task priorities correct?
Is the buffer sufficient?

3. Adjust Schedule

Move delayed tasks to next week
If new tasks arise, cut or postpone something
If there's room, consider advancing tasks

Review Timing

Friday evening: Look back on the week
Sunday night: Confirm next week's plan

This routine alone drastically reduces last-minute panic.

Using Digital Tools and Analog Planners

Both digital tools and analog planners have strengths for schedule management.

What Digital Tools Excel At

Reminder and notification features
Sharing and syncing with multiple people
Long-term project management
Reordering and moving tasks

Recommended tools:

Google Calendar: Managing deadlines and meetings
Notion: Visualizing entire projects
Todoist: Task list management

What Analog Planners Excel At

Memory retention through handwriting
Easy to overview everything
Device-independent
Free memos and diagrams

Recommended types:

Vertical (timeline) planners: Visualize daily time schedule
Gantt chart planners: See entire project at a glance

Hybrid Operation

Digital: Deadlines, recurring meetings, reminders
Analog: Daily task lists, reflection memos

Leveraging the strengths of both achieves the most efficient management.

Managing Deadlines and Milestones with a Date Calculator

When creating a reverse schedule, calculations like "what date is 3 weeks before the deadline?" or "when is 10 business days from now?" are needed.

Using a date calculator:

Instantly calculate 〇 days before deadline
Reverse calculate on business-day basis, excluding weekends/holidays
Batch calculate multiple milestone dates

Example: If deadline is June 30, 2026

3 weeks before (21 days): June 9
2 weeks before (14 days): June 16
1 week before (7 days): June 23
3 business days before: June 25 (Fri)

Placing major milestones on these dates makes the reverse schedule concrete at once.

Summary: "Breathing Room" Is Created by Design, Not Effort

People who don't get chased by deadlines aren't "good at time management"—they're "good at schedule design."

Understand planning fallacy and avoid optimistic estimates
Set milestones by working backward from the goal
Secure 20% of work time as buffer
Improve estimation accuracy with time tracking
Maintain realistic plans with weekly reviews
Use digital and analog tools strategically

"Panicking just before the deadline" isn't a personality issue—it's a planning issue. By mastering reverse planning and buffer allocation, anyone can achieve a "comfortable schedule."

Use the date calculator too, and practice project management with breathing room.

Stop Chasing Deadlines: How to Build a Comfortable Schedule with Reverse Planning