late start and finish times
To perform the backward pass you will start with the last activity in the network and continue until you have reached the first activity in the network.
The first step in the backward pass is to copy the Early Finish Time of the last activity in the schedule to the Late Finish Time of the last activity in the schedule. If you have a project completion date, then use the overall project completion date for the last activity’s Late Finish Time.
Once the last activity’s Late Finish Time has been set, then you can calculate the activity’s Late Start Time by subtracting the activity duration from the Late Finish Date. As you proceed through the schedule the Late Finish Time of a preceding activity is the earliest of the prior Late Start Times.
In this first example schedule, each activity has only a single following activity, therefore, the schedule calculation is quite simple. In the second example there is an activity with multiple priors. Notice that the earliest of the following Late Start Times are set as the Late Finish Time of the prior activity.
