Change Hours/Day in Calendar but keep Activity Duration unchanged in Primavera P6

When scheduling in Primavera P6, you may start with an 8-hour/day calendar. If you later switch to a 10-hour/day calendar, you’ll notice that activity durations and the project completion date change. For example, a 10-day activity becomes 8 days because the total hours remain the same, but the daily work hours increase.

So how can you change the calendar from 8 to 10 hours/day without changing the activity durations?

Step-by-Step Guide

1. Open Global Change

Go to: Tools → Global Change

Click New to create a new global change rule.

2. Create the Rule

Set up the rule to adjust the activity duration like the following picture:

3. Preview and Apply

Click Change to preview the results. Primavera will show you how the durations will be updated.

If everything looks correct, click Commit Change.

4. Verify the Result

After applying the change, you’ll see:

• Activity durations are restored to their original values (e.g., back to 10 days).
• The project completion date remains unchanged.
• The calendar now reflects 10 hours/day.