Introduction :
Primavera P6 does not decide delay by looking at red bars or late dates. It calculates delay using scheduling logic that runs silently every time the schedule is updated. Anyone taking a Primavera P6 Course quickly learns how to enter activities, durations, and links. But very few users understand how the software really decides that a project is delayed. Primavera does not store delay as a value. It recalculates delay again and again using time flow rules, logic relationships, calendars, and remaining work. This is why delay results often confuse planners who rely only on screen views and reports.
How Primavera Uses Time Flow Instead of Dates?
Primavera P6 does not think in terms of calendar dates first. It thinks in terms of time movement through a network. Every activity passes time to the next activity based on logic rules. This process is called time propagation.
When you run the schedule, Primavera performs two major calculations:
- Forward pass
- Backward pass
The forward pass calculates early start and early finish dates. The backward pass calculates late start and late finish dates. Delay is identified only when the forward pass pushes the project end date beyond its planned finish.
If an activity finishes late but does not push time forward to the end of the project, Primavera does not mark it as a delay. It marks it as float usage.
Important points many users miss:
- Primavera does not check “planned vs actual” directly
- It checks whether logic allows time to move further
- Delay is a result of logic pressure, not late work alone
In complex schedules used in NCR regions, especially after Primavera P6 Training in Noida, planners notice that delays often appear far away from where work slowed down. This happens because time flows through logic, not through locations or teams.
Float Is Not Protection, It Is a Calculation Result
Float is often misunderstood. Many think float is a safe time given by the planner. That is wrong. Float is calculated by Primavera after every schedule run.
Primavera calculates float using early and late dates. If logic changes, float changes. If calendars change, float changes. If one successor slips, float reduces everywhere upstream.
Key technical facts about float:
- Total Float = Late Finish – Early Finish
- Free Float depends on successor early dates
- Float is recalculated after every update
- Float can disappear without any new delay
Because of this, float should never be treated as a guaranteed buffer.
In large construction and IT infrastructure schedules used across Delhi NCR, planners trained at a Primavera P6 Training Institute in Delhi often face float collapse when multiple contractors update progress late. This is not a software issue. It is how CPM math works.
Longest Path Logic Controls Real Delay
Primavera P6 does not rely only on classic critical path. It uses Longest Path logic. This means it finds the chain of activities with the longest remaining duration to the project end.
An activity may still show positive float and yet lie on the longest path. If that activity slips, the project finish date slips.
This is why relying only on zero-float activities gives wrong delay analysis.
How longest path affects delay:
- It considers remaining duration, not original duration
- It considers calendars and constraints
- It updates after every data date change
- It can change even without logic edits
This behavior is common in fast-track projects where activities overlap. In Noida’s commercial and data center projects, planners using Primavera P6 Training in Noida often deal with schedules where procurement or approvals suddenly become delayed drivers even when site work is ongoing.
How Calendars and Constraints Distort Delay Results
Calendars define working time. If two linked activities use different calendars, time does not flow evenly. A five-day calendar activity can delay a six-day calendar successor even if durations look fine.
Constraints are even more dangerous. Hard constraints force dates and block logic.
Common constraint impacts:
- “Finish On” hides real critical path
- “Must Finish By” creates artificial float
- Constraints shift delay to other paths
Out-of-sequence progress is another major factor. When work starts before predecessors finish, Primavera must choose how to handle logic.
There are two options:
- Retained Logic: shows delay honestly
- Progress Override: hides delay by breaking logic
Most planners unknowingly use progress override and think delay is resolved.
In Delhi NCR projects handled by multiple vendors, schedules reviewed after Primavera P6 Training Institute in Delhi sessions often show hidden delays caused by incorrect progress settings and forced dates.
Internal Factors That Trigger Delay in Primavera
The table below shows what actually causes delay inside Primavera, not what users assume.
| Factor | How It Influences Delay |
| Logic Relationships | Control how time flows |
| Remaining Duration | Drives longest path |
| Activity Calendars | Change working time |
| Constraints | Override logic rules |
| Out-of-Sequence Progress | Alters delay visibility |
| Data Date Movement | Forces full recalculation |
Delay is never based on one factor alone. It is always a combination.
Why Delay Keeps Shifting in Updates
Many users complain that the delay “moves” every week. One update shows delay in design. The next update shows it in installation. This is expected behavior.
Primavera recalculates delay from the data date forward. I do not remember where the delay started. It only shows where delay pressure currently exists.
This shifting helps identify where recovery effort is needed now, not where mistakes happened earlier.
Skipping updates makes this worse. When schedules are updated monthly instead of weekly, delay appears sudden and severe.
How Recovery Actions Affect Delay Calculation
Primavera does not understand intent. It understands logic. If recovery actions are not reflected correctly in logic and duration, delay remains.
- Fast-tracking must change logic
- Crashing must change duration
- Overtime must change calendars
If these are not updated correctly, Primavera continues to show delay even if site progress improves.
This is why technical scheduling knowledge matters more than reporting skills.
Key Takeaways
- Primavera calculates delay through logic, not visuals
- Float is dynamic and not guaranteed
- Longest path controls project finish
- Calendars and constraints can hide or exaggerate delay
- Delay shifts because Primavera recalculates every update
- Recovery must be entered logically to reflect results
Sum up,
Primavera P6 calculates delay using strict CPM logic, longest path rules, and continuous recalculation. Delay is never stored as a value. It is always derived from logic, float, calendars, and remaining work. Users who treat Primavera as a data entry tool often misunderstand delay reports. Those who understand its internal logic gain real control over schedules, forecasts, and recovery plans.
