Evidence-based Scheduling is based on at least two core ideas: including all time spent, and using a Monte Carlo completion date prediction method.
Similarly, as Spolsky points out,[2] your bosses' stories about his fishing trips, or model helicopter, are both a time-sink and politically dangerous to put on a time-reporting system.
The key insight in evidence-based scheduling is that the only thing which needs measuring is the actual delivery of tasks.
The reasons for anomalies may come out if the organisation wishes to dig deeper into why people have irregular estimates.
Another core idea is the use of the Monte Carlo method to predict project completion dates.