The problem is that date estimates for deadlines are NOT a standard distribution and everybody's normal statistical tools do not work. They are pretty much a o

The problem is that date estimates for deadlines are NOT a standard distribution and everybody's normal statistical tools do not work. They are pretty much a one sided distribution power law. Deadlines almost never come in early and, when they do, it's rarely by much. On the other hand, deadlines can come in late by wild amounts. Generating confidence intervals on that is really hard.