How to Set Up Overnight Shift Calendars in Microsoft Project
Question details
The user needs to accurately calculate task durations for overnight shifts in Microsoft Project without experiencing scheduling and calculation errors.
- Product
- Microsoft Project
- Device & OS
- not provided
- Scenario
- Planning tasks and assigning resources for work shifts that cross over midnight into the next working day (e.g., 7:00 PM to 5:30 AM).
- Observed behavior
- Microsoft Project calculates overnight task durations incorrectly when standard working hours are applied, as it struggles to recognize shifts that span across two different calendar days.
Ensure you have your project's date format configured to display both dates and times (e.g., mm/dd/yy hh:mm) in the General Options, allowing you to accurately verify the start and finish times of overnight tasks.
Create and Assign Custom Night Shift Calendars
Properly defining working hours past midnight and assigning dedicated base calendars to night-shift resources prevents duration calculation errors.
To handle overnight shifts accurately, you must create distinct calendars for day and night shifts while keeping the default 'Hours per day' project setting untouched. By entering durations in hours and applying the specific calendars to your resources, Microsoft Project will calculate the timeline seamlessly.
Go to File > Options > Schedule. Keep the 'Hours per day' setting at the default 8 hours. Ensure you enter all task durations in working hours (e.g., '10h' instead of '1d') to maintain accuracy.
Navigate to Project > Change Working Time. Click 'Create New Calendar', choose to make a copy of the Standard calendar, and name it 'Night Shift'.
In the 'Work Weeks' tab, click 'Details'. Select the working days and set the specific working times to reflect the night shift crossing midnight (e.g., 7:00 PM to 12:00 AM, and 12:00 AM to 5:30 AM).
Switch to the Resource Sheet view. In the 'Base Calendar' column, select the newly created 'Night Shift' calendar for all applicable night shift resources.
Go to your Gantt Chart, double-click the overnight task, and use the Resources tab to assign your night-shift resource. The task will now schedule according to the night shift working hours.
Use the 24-Hour Calendar for Continuous Tasks
Use this method only for specific tasks that genuinely run continuously 24/7 without scheduled breaks or shift changes.
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Frequently Asked Questions
Why does Microsoft Project calculate my night shift duration as 2 days instead of 1?
This happens because the standard project calendar defines a working day from 8:00 AM to 5:00 PM. When a task crosses midnight, Project schedules it across two separate standard working days. Creating a custom night shift calendar with hours that span past midnight resolves this discrepancy.
Should I change the 'Hours per day' setting for night shifts?
No, it is highly recommended to keep the default definition of a working day (usually 8 hours) in File > Options > Schedule. Instead of changing this global setting, enter your task durations in hours (e.g., '10h') and apply specific base calendars to your resources.
How can I check if my overnight task is scheduled correctly?
First, change your date format to display both dates and times (File > Options > General). Then, switch to the Resource Usage or Task Usage view to inspect the time-phased data, ensuring the assigned work hours fall exactly within the expected evening and morning hours.
Can I just use the built-in 24-hour calendar for night shifts?
The 24-hour calendar should only be used for tasks that run continuously 24/7. Assigning it to human resources working a specific night shift (e.g., 7:00 PM to 5:30 AM) will cause scheduling inaccuracies and overallocation warnings, as the software will assume the resource never stops working.
