Hello Peter,

1. ES: The Early Start date of an activity is the earliest point in time when the activity can logically begin based on its predecessors and any constraints.

2. LS: The Late Start date of an activity is the latest point in time by which an activity must start to avoid delaying the project finish date.

3. EF: The Early Finish date of an activity is the earliest point in time when the activity can logically be completed based on its ES and duration.

4. LF: The Late Finish date of an activity is the latest point in time by which an activity must finish to avoid delaying the project finish date.

5. PS: The Planned Start date of an activity is often user-defined and represents the initially planned or baseline start date for the activity.

6. PF: The Planned Finish date of an activity is user-defined and represents the initially planned or baseline finish date for the activity.

Critical Path: Activities that have zero float (difference between LF and EF, or LS and ES) are on the critical path. The critical path determines the minimum project duration and any delay in critical path activities will directly delay the project finish date.

These date fields (ES, LS, PS, EF, LF, PF) are fundamental in project scheduling software as they provide crucial information about activity timing, dependencies, flexibility, and criticality. Understanding how these fields are calculated and their significance helps schedulers in managing and controlling project schedules effectively.

Thanks,