Project Tip: Non Fixed-Duration Tasks

Did you know this little feature of MS Project?

For a non fixed-duration task, let us say that you enter a start date of May 7th and a finish date of May 9th, Project calculates the duration as three days.  If you change the finish date to May 11th, the duration is recalculated to five days. Correct?  All right that seems fair.  For example, if you enter a start date of May 1 and a finish date of May 4, Project calculates the duration as three days. If you change the finish date to May 5, the duration is recalculated to four days. But if you change the finish date to May 8 instead of editing the duration, Project recalculates the start date to May 4, keeping the duration constant at four days because the last two fields that you changed were for the finish date and duration.

If you start with..
Start Date:   Finish Date:    Duration:
May 7           May 9              3 days

Change the Finish Date to May 11…
Start Date:   Finish Date:    Duration:
May 7           May 11            5 days

But now, if you change the duration to 10 days instead of editing the start and finish dates - what happens to the task?

Well actually Project recalculates the start date to back to May 1 because the last two fields that you changed were for the finish date and duration.  Thus the start date is changed to May 1st.

Changing the Finish Date to May 8th…
Start Date:   Finish Date:    Duration:
May 1           May 11            10 days

Symptoms:
A task's duration (The total span of active working time that is required to complete a task. This is generally the amount of working time from the start to finish of a task, as defined by the project and resource calendar.) changes when you change its start (The date when a task is scheduled to begin. This date is based on the duration, calendars, and constraints of predecessor and successor tasks. A task's start date is also based on its own calendars and constraints.) and finish (The date that a task is scheduled to be completed. This date is based on the task's start date, duration, calendars, predecessor dates, task dependencies, and constraints.) dates.

Cause:
If you enter a task's start and finish dates instead of a duration, Project calculates the duration based on the working time (Hours designated in a resource or project calendar during which work can occur.) between those dates. If you later change the start date or finish date (but don't change the duration), the duration is recalculated.

!!!! OF A TASK'S DURATION, START DATE, AND FINISH DATE FIELDS, PROJECT TRACKS THE LAST TWO FIELDS THAT WERE EDITED AND RECALCULATES THE EARLIEST EDITED OF THOSE THREE FIELDS BASED ON THE LATEST FIELD THAT YOU CHANGED. SO IF YOU ENTER A START DATE AND THEN ENTER A FINISH DATE, THE DURATION IS CALCULATED. IF YOU THEN CHANGE THE DURATION, THE START DATE IS RECALCULATED !!!!

Resolution:
If you must enter start and finish dates, and if you want the duration to remain constant, make sure the new start and finish dates represent the same number of working days as the previous dates. The duration will remain the same as before.

Comments

[Santosh]

Hi,
I am having Project manager access on Project Server and i have assigned some tasks to some resources, from 3/6 to 3/12, under following catagories:
Fixed Duration effort driven,
Fixed Duration effort driven,
Fixed Units effort driven,
Fixed Units non effort driven,
Fixed Work
One of the resources enterd his work hrs starting from 3/8 and submitted the task. Its affecting the actual start date and finish date, ie. 3/6 & 3/12 to 3/8 & 3/14.
How should I restrict that?
please guide me.