Douglas Hofstadter in his book, Escher, Bach: An Eternal Golden Braid (1979) named Hofstadter’s Law which states:
“It always takes longer than you expect, even when you take into account Hofstadter’s Law.”
Complex and/or infrequent tasks take a longer time to complete than estimated. We are generally bad at estimating the time it will take to complete a task, primarily due to overconfidence.
The law itself is self-referential: Hofstadter’s Law is stated in its own law, implying a circular loop.
A prudent but crude projection of the time it will take to complete a task is to multiply the original estimate by three. So for something that you think will take an hour, allocate three hours.
Another more absurd projection is to estimate time to complete the task, double the estimate and then move to the next largest incremental time factor:
Second -> Minute ->Hour -> Day -> Week -> Month -> Year -> Decade -> Century
So something that you think will take two days will take four weeks.
You have a choice of when to call a project “done.” A task will still take longer than originally planned. The difference between it taking 3 times longer rather than 10 times longer is this “good enough” distinction.
When confronted with an estimate to complete a task, remember Hofstadter’s Law end expect much longer.