Fundamentals of Project Management, Third Edition

Schedule Computations

Normally, you would let a computer do these computations for you, so you may wonder why it is necessary to know how to do them manually. My belief is that unless you know how the computations are done, you do not fully understand the meanings of float, early and late dates, and so on. Further, you can easily fall prey to the garbage-in, garbage-out malady. So here is a brief treatment of how the calculations are done by the computer. (For most schedules, the computer has the added bonus of converting times to calendar dates, which is no easy task to do manually.)

First, consider what we want to know about the project. If it starts at some time = zero, we want to know how soon it can be finished. Naturally, in most actual ...