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Fix Microsoft Project Tasks Scheduled During Nonworking Hours

Elise Williams Oct 23, 2026 869 views

Question details

The user needs to troubleshoot Microsoft Project schedules that incorrectly place tasks outside of configured working hours, such as overnight or on weekends.

Fix Microsoft Project Tasks Scheduled During Nonworking Hours

Product: Microsoft Project
Device & OS: not provided
Scenario: Managing project timelines where scheduled tasks are automatically shifted into nonworking times despite default scheduling expectations.
Observed behavior: Tasks are scheduled during nonworking time (overnight or weekends), often due to conflicting project, task, or resource base calendars.

Before you start

Ensure you have full edit access to the project file and document your organization's exact standard working hours before modifying global calendar and schedule options.

Solution 1Recommended

Adjust Project Calendar and Global Schedule Options

Verify and align the project's base calendar, daily schedule options, and start times to prevent tasks from spilling into nonworking hours.

Microsoft Project relies on strict calendar rules. If your default working hours in the schedule options do not match the applied project calendar, tasks may start or end at unexpected times.

Match daily work hours

Navigate to File > Options > Schedule. Set the 'Hours per day' to match your actual scheduled workday (for example, 9:00 AM to 4:00 PM).

Set the correct project calendar

Go to Project > Project Information in the top ribbon. Under the Calendar dropdown, ensure your intended custom calendar is selected instead of the default.

Adjust project start time

In the Project Information dialog, verify that the project start time matches your workday start (e.g., 9:00 AM) instead of the default 8:00 AM.

Update date format

Go back to File > Options > General. Under the Date format dropdown, select a format that includes both the date and the time of day to easily spot scheduling anomalies.

Adjust Project Calendar and Global Schedule Options

Configuration Alignment: Matching your 'Hours per day' with your base calendar working times is the most critical step to ensure stable project scheduling.

Solution 2

Resolve Resource and Task Calendar Conflicts

Conflicting calendars at the resource or task level can override the main project calendar, causing unexpected weekend or overnight scheduling.

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Frequently Asked Questions

Why does Microsoft Project schedule my tasks on weekends?

This usually happens when the assigned resource base calendar or specific task calendar is configured to treat weekends as working days, overriding your main project calendar settings.

How do I change the default start time in Microsoft Project?

Navigate to File > Options > Schedule, and update the 'Default start time' field to your desired hour, such as 9:00 AM instead of the standard 8:00 AM.

Can conflicting task and resource calendars cause schedule instability?

Yes. If a task is assigned a specific calendar that conflicts with the assigned resource's base calendar, Microsoft Project may schedule tasks unexpectedly during nonworking hours. Ensure alignment across project, task, and resource calendars.

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