BL Start Date, Early Start , and Late Start in Primavera P6

In project management, understanding the various types of start dates is important for effective scheduling and tracking. This article compares the Planned Start Date, Baseline Start Date, Early Start Date, Start Date, and Late Start Date, offering insights into their roles in managing project timelines.

1.      BL Project Start:

o    The Baseline Start Date is the start date that was established when the project baseline was set. It represents the original target or planned start date at the time the baseline was created.

o    The BL Project Start Date does not change unless the baseline itself is updated or revised. It serves as a reference point to compare the current schedule against the original plan and helps in measuring schedule performance.

2.      Planned Start:

o The planned dates are useful for comparing current and planned progress for an activity if you are not using baselines. While an activity is not started, the planned start for an activity is the same as the early start and is recalculated whenever you reschedule the project. When you apply an actual start to an activity, the planned start is fixed and no longer recalculated.

o  This is the date that Primavera calculates for the start of an activity based on the current schedule. It reflects the date that the project team expects the activity to start, considering current project progress, constraints, and logic.

o  The Planned Start Date may change throughout the project as the schedule is updated with new information or if delays or changes occur.

    3. Start 

• • • For the Completed and In Progress Activities, It’s the Actual Start date and has an A beside the Date, For the Not Started Activities, it’s the Planned Start for the activity or the BL Project start if you don’t have any negative float.

• • • The current scheduled start date of an activity in the project plan, Calculated based on schedule logic (relationships, constraints, and calendars). It may be a forecast Start date or Actual Start.

4.      Early Start:

o    The Early Start Date is the earliest possible date that an activity can begin, based on the current project logic and constraints.

o    It is determined by forward scheduling calculations, considering dependencies, duration, and constraints.

o    This date can shift as the project progresses and as new information or delays are introduced. It will mainly be equal to the start date

o    This date will always equal the planned date on which the activity has zero total float.

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5.      Late Start:

o    The Late Start Date is the latest possible date that an activity can start without delaying the project’s completion.

o    It is determined by backward scheduling calculations and is critical for understanding float in the schedule.

o    If an activity starts later than this date, it may delay the overall project completion.

“The same applies to the Finish Dates.”

In the above picture, The dates are not equal for In Progress activities, but for the Not Started  Activities with a Float, furthermore the late Start differs from all the start dates.

Note: This is an Updated Schedule so the BL Project Start, Planned Start, Start, and Early Start are not equal due to some delays. However, In the Baseline schedule, all these Dates will be equal.

So, let’s take a look at A2150 Activity

BL Project Start Date: It’s the start date of this activity in the baseline assigned Schedule.

Planned Start Date: This date reflects the latest planned start date calculated by P6 before applying actuals. For example, in this activity, which started on 24 Oct, the planned start date was 22 Feb before applying the actual start date. The planned start date is fixed as we applied an actual start date

Start Date: This Date is the actual start date for the activity, as it has an A on the date.

Early Start: This date is the early start date for the activity according to the driving relationship.

Late Start: This date is the early start date, plus the Total float of the activity.

Early and Late Cashflow

When drawing a cash flow curve based on the Early Start and Late Start dates in Primavera P6, the main focus is on how costs are distributed across time, reflecting either an optimistic or a delayed payments scenario. Here’s how these two scheduling perspectives influence cash flow:

1. Cash Flow Based on Early Start

• • Definition: Reflects cash flow assuming all activities begin at their earliest possible start dates.
  • Key Features:
    • Represents an optimistic scenario where work progresses without delays.
    • Cash outflows occur earlier in the project timeline because activities start as soon as possible.
  • Advantages:
    • Identifies peak funding requirements earlier in the project.
  • Disadvantages:
    • May not account for practical constraints like resource availability or funding limitations.

2. Cash Flow Based on Late Start

• • Definition: Reflects cash flow assuming all activities begin at their latest possible start dates, without affecting the project finish date.
  • Key Features:
    • Represents a delayed scenario, And pushing expenses later in the timeline.
    • Cash outflows occur closer to the project finish date, creating a flatter initial cash flow curve.
    • Useful for deferring costs to align with delayed funding or to minimize early financial commitments.
  • Advantages:
    • Helps preserve cash flow early in the project, aligning costs with funding availability.
    • Can be useful for risk mitigation, leaving flexibility for unexpected changes.
  • Disadvantages:
    • Increases the risk of compressed schedules and resource conflicts later in the project.

The banana shape in the above histogram arises when plotting two cumulative curves—one based on Early Start dates and the other on Late Start dates—for activities in a project schedule. This shape represents the schedule’s variability or flexibility and highlights the range of possible cumulative progress over time.

1. 1. Early Start Curve:

      • It  represents the cumulative progress or cash flow if all activities start and finish as early as possible.
      • Forms the Lower Curve of the cumulative histogram since it assumes the quickest progression.

   2. Late Start Curve:

      • It represents the cumulative progress or cash flow if all activities start and finish as late as possible, And without delaying the project’s overall finish date.
      • Forms the Upper Curve of the cumulative histogram since it assumes the latest feasible progress.

   3. Banana Shape:

      • The gap between these two curves creates the “banana”—a visualization of the schedule’s total float across activities.
      • This area highlights the degree of flexibility in the schedule:
        • A wider gap indicates higher float and more flexibility.
        • A narrower gap suggests tighter scheduling with less room for delays.

To know how to draw the banana curve in P6, Read this Article: https://planningengineer.net/how-to-create-early-curve-and-late-curve-from-primavera-p6/

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