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How to Prevent Duration Changes When Unlinking Microsoft Project Subprojects

WPS Editor Sep 27, 2026 868 views

Question details

Users need a way to unlink subprojects from a Microsoft Project master schedule without causing unintended task duration changes.

How to Prevent Project Duration Changes After Removing Subproject Links

Product: Microsoft Project
Device & OS: not provided
Scenario: Managing a master schedule with multiple subprojects containing various working-time calendars and shifts.
Observed behavior: Task durations automatically change and recalculate when the dynamic links between the master project and subprojects are broken due to mismatched calendar settings.

Before you start

Before breaking any dynamic links in your master project, ensure you have backed up all schedule files and documented the exact working-time calendars currently used across all subprojects.

Solution 1Recommended

Standardize Calendars and Adjust Duration Inputs

Aligning calendar settings across the master and subprojects prevents recalculations when unlinking.

When subprojects use different calendars (such as 8, 10, 12, or 24-hour shifts) compared to the master project, MS Project recalculates durations based on the master's default working day once links are broken. Standardizing these calendars prevents this mismatch.

Access working time settings

Open the master project, navigate to the 'Project' tab on the ribbon, and select 'Change Working Time'.

Standardize working hours

Review the working day lengths, shift times, and exceptions, ensuring they perfectly align with the calendars set in your individual subprojects.

Update schedule options

Go to File > Options > Schedule and ensure the 'Hours per day' value matches the standardized calendar structure.

Enter durations in hours

Instead of defining durations in days, enter all task durations in hours (e.g., type '24h' instead of '3d') to force the software to respect absolute time rather than variable daily schedules.

Standardize Calendars and Adjust Duration Inputs

Best Practice: Using hours instead of days for task durations eliminates ambiguity when dealing with multiple shifts or contractors with varying schedules.

Solution 2

Keep Subprojects Linked in a Stable Environment

If time constraints prevent you from standardizing complex calendars, maintaining the dynamic links in a highly controlled environment is the safest alternative.

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Frequently Asked Questions

Why do task durations change when I unlink a subproject in Microsoft Project?

This occurs when the subproject and master project use different working-time calendars. Upon unlinking, the tasks revert to the master project's default calendar, causing MS Project to recalculate task durations based on different daily working hours.

Can I use SharePoint to host dynamically linked master and subprojects?

It is highly discouraged. Dynamically linked Project structures often become corrupted when stored on SharePoint or remote web servers. It is best to keep them in a single folder on a local drive or a stable shared network drive.

How can I accurately record task durations when dealing with multiple shift schedules?

When managing multiple shifts (such as 8, 10, 12, or 24-hour schedules), it is best to enter task durations in absolute hours (e.g., '40h') rather than days ('5d'). This prevents the software from recalculating durations based on a generic 8-hour workday assumption.

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