Latest finish time (LF) is the latest point at which an activity can be completed without delaying the project's overall completion. It is determined during a backward pass through the activity network. section 13.3 section 13.3.2
Calculate and interpret LF through these relationships:
- Set the final activity's LF to the project completion time, then move backward through the network. section 13.3.2
- For an activity with one successor, set LF to that successor's latest start time. section 13.3.2
- For multiple successors, use the minimum of their latest start times as the activity's LF. section 13.3.2
- Calculate latest start time as LS = LF − activity duration; compare LF with earliest finish to determine finish-time slack. section 13.3.2 section 13.3.3
Automated reporting tool
The project finishes at week 29, so Activity L has LF = 29 and LS = 27 for its two-week duration. Activity K then has LF = 27 and LS = 24 for its three-week duration. Both activities have zero slack and lie on the critical path. section 13.3.2 section 13.3.3
Figure 13.3 A second visual representation of the automated reporting tool project plan. The new three-digit sequence for each activity represents, in order, the latest start time, the expected duration, and the latest finish time. A quick and easy way of distinguishing critical tasks from noncritical tasks is to compare the three-digit sequences: critical tasks have similar three-digit sequences, whereas noncritical tasks do not.
Use the network diagram to compare latest-start, duration, and latest-finish sequences and distinguish critical from noncritical activities. section 13.3.2
