A’ight, Bruv. Five minute job, three hours later — the oldest lie we tell ourselves.
Last weekend, I decided to reorganise my desk cables. One drawer. Maybe 15 minutes. That was the estimate. Three hours later, I was sitting on the floor surrounded by a nest of ethernet cables, USB extensions, and one mysterious power adapter that I am 60% sure belongs to a printer I no longer own. The drawer was not organised. The drawer was emptied. The mess had simply relocated from the drawer to the floor. And I had lost an entire Saturday afternoon to a task I genuinely believed would take 15 minutes.
This is not a personal failing. Well, it is a personal failing. But it is also a documented psychological phenomenon called the planning fallacy — our chronic tendency to underestimate how long things will take, even when we have done those exact things before and should by all logic know better. Humans are terrible at estimating time. We are especially terrible at estimating time for things we have already done. The more familiar the task, the more optimistic the estimate. It is one of the most reliable cognitive biases ever studied. And it ruins weekends.
The IT department is a planning fallacy museum
I work in IT. If you want to see the planning fallacy in its natural habitat, spend a week in any technology department. Every project starts with an estimate. Every estimate is wrong. Not sometimes wrong. Systematically wrong. A server migration that is supposed to take a weekend takes a week. A software update that is “just a patch” breaks three other systems. A “quick database fix” that someone estimated at 30 minutes consumes the entire morning and two people’s sanity.
The fascinating thing is that this happens even when the same team has done the same type of migration before. They know — from direct, painful experience — that these things never go according to plan. And yet, when asked for an estimate on the next one, they will confidently say “should be done by Friday” with the same optimism as the last five times, all of which stretched into the following Wednesday. The planning fallacy survives direct experience. That is how deep it runs.
Your brain is an optimist — not a realist
The psychologists who study this — Daniel Kahneman and Amos Tversky, the Batman and Robin of cognitive bias research — figured out what is happening. When you estimate how long something will take, your brain constructs a mental simulation of the task. You visualise the steps. And in that simulation, everything goes perfectly. No interruptions. No unexpected complications. No missing parts. No “wait, this cable is the wrong type” moments. Just smooth, frictionless progress from start to finish.
This is called taking the “inside view.” You are inside the problem, imagining the best-case sequence of events. What you should be doing is taking the “outside view” — looking at how long similar tasks actually took in the past, for you and for other people. But your brain hates the outside view. The outside view is boring. The outside view involves admitting that you are average. The inside view is exciting. The inside view is a movie where you are the competent protagonist who finishes everything on time. Your brain prefers the movie. The movie is a lie.
The one trick that actually works
There is exactly one method that has been shown to improve time estimates, and I am going to tell you what it is even though you will not use it. It is called “reference class forecasting.” Instead of asking “how long will this take?” you ask “how long did similar tasks take last time?” Then you use that as your baseline. Not your optimistic internal simulation. The actual historical data. The cold, unflattering, “last time this took four hours” data.
The reason you will not use this method is the same reason I did not use it before tackling my desk drawer. Because accepting the outside view means accepting that you are not special. That your cable drawer is not uniquely organised. That your project is not uniquely simple. That you, like every human who has ever lived, will encounter unexpected complications. And nobody wants to build that into their estimate. Optimism feels better. Until you are sitting on the floor at 5 PM surrounded by cables, wondering where your Saturday went. The planning fallacy always collects its debt. The only question is whether you budget for it. XAXAXA!