Wait, you might be thinking, this doesn’t make sense. A task takes as long as it takes. Why would that change depending on what you write down on your schedule?

“Work expands to fill the time allotted,” explains Ellen Faye, a productivity coach and author of Productivity For How You’re Wired. “It happens because people don’t give thought to the value of their time and then they don’t assess how much time the task they are working on is worthy of.

“Another principle – the Pareto principle (also known as the 80/20 rule) – comes into play here. Pareto’s principle implies that you get 80% of the results with 20% of the time or effort. That can be interpreted that you can get to 80% (above average, if we were grading this) with 20% of the time. I see this often: you can put in an hour and get to very good, but to get to excellent/100%/almost perfect (since perfect isn’t a thing) it takes five hours.

“We’re not good at or don’t estimate the amount of time needed for a particular task,” Evans adds. “We don’t always limit the time a task will take; instead, we work on it until it’s complete. It also happens when we’re not prioritising the importance of a task and allocating an appropriate amount of time, spending too long on trivial tasks or believing we have more time available than we really do.

“If you have unlimited time or a significant amount of time to complete a task, you’ll either put off working on the task, because you have plenty of time, or you lose focus and get distracted by other random tasks, which means the task takes longer. It also happens the other way around. We think something will take 10 minutes and it actually takes 30. Allocate a day and we end up needing two.”

Parkinson’s law is the concept that could help you feel more in control of time – here’s how to use it to your advantage