How long does it take to get the work done?

When trying to estimate the time you need to get something done, there are some laws you might need to consider. In fact, it turns out not to be a question of efficiency or productivity, but of our inevitable human nature.

Hofstadter's Law: It always takes longer than you expect, even when you take into account Hofstadter's Law.
Coined by Douglas Hofstadter in 1979, this law tells us the reality of planning fallacy. Neil D. Weinstein's researches in the 1980s discovered that the majority of people are actually egocentric and therefore tend to have an unrealistic positive belief about their future (called "Optimistic Bias"). Underestimating the probability of negative events certainly leads to miscalculating time. Half-jokingly, Hofstadter offered a rule for correction: double the number and step up to the next higher units. For example, a job estimated at 1 hour can be accomplished in 2 days, while a 3-month project will take you 6 years.

Parkinson's Law: Work expands so as to fill the time available for its completion.
Cyril Northcote Parkinson stated this law in his 1955 article in The Economist, followed by statistical evidences drawn from his historical research, such as the fact that from 1914 to 1928, the number of British Admiralty officials increased almost 80% while the Navy diminished by a third in men and two-thirds in ships; and also the increase of the Colonial Office staff during the decline of the British Empire. Parkinson explained these with two motive forces: an official wants to multiply subordinates, not rivals; and officials make work for each other. Have you ever had the feeling that your team leader was always trying to get more people on the team, and would always come up with something for you whenever you were just about to open your web browser?

Student syndrome: Many people will start to fully apply themselves to a task just at the last possible moment before a deadline.
We've all been students and we all remember how we dealt with the long-term assignments. We might start early, but the last minute would most likely be stressful anyways. You may think procrastination relates to either laziness or perfectionism. Psychologically, it's just caused by two basic human tendencies: we would relax when things seem easy and try to avoid the things that seem to be difficult. That's why it's so hard to start organizing a messy room or working on the portfolio. Some scholars also pointed out the importance of motivation. If the task is boring or I don't feel rewarded for doing it, why would I spend time on it now when there is so much fun out there?

OK, how long does it take to get it done? I guess the perfect answer would be "When is it due?"