Why are my Finish Dates Changing on my Fixed Duration Tasks in MS Project?

Many project managers who’ve previously worked in a Primavera environment, but who are now operating in a Microsoft Project Server system / Project Online, like to use Fixed Duration tasks because their behaviour is more like the behaviour of tasks in Primavera. However, many project managers also assume that if a task is a Fixed Duration task, then the Duration of the task will never change, and the Finish date of the task will never change as well. Unfortunately, both of these assumptions are wrong!

In fact, there are a number of conditions which can cause the Duration value and Finish date to change on a Fixed Duration task. These conditions include, but are not limited, to the following:
• A team member submits planned nonworking time, such as vacation, for a time period between the Start date and Finish date of the Fixed Duration task.
• An assigned team member enters an initial Actual Work value on a date later than the Start date of the Fixed Duration task.
• A team member increases the Remaining Work value after completing the planned work on the task.
• A team member does not finish assigned work by the Finish date of the task.
• A team member enters an Actual Work value on a date later than the Finish date of the task.
• A team member enters progress earlier than the Start date of the task, but the task has a Finish No Earlier Than (FNET) or Must Finish On (MFO) constraint.
• The project manager reschedules uncompleted work from the past to the current reporting period.

As you can clearly see from the list of conditions above, you simply cannot prevent Microsoft Project from changing the Duration value and/or the Finish date of Fixed Duration tasks when these conditions occur. Now, though, you should have an idea of where to look within your schedules to determine cause.

Good luck, and happy scheduling!
-Todd Meier

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