Compare schedules when you need to explain what changed between two plans or reporting periods. Preserve both files first: a comparison needs two distinct schedule states.

Choose the right comparison

Comparison reads the schedules. It does not merge them, overwrite either file, or make the reference Current.

Compare two files

1. Open the project’s Files page and choose Compare.
2. Set Current schedule (newer) to the new submission or revised plan.
3. Set Previous schedule (older) to the reference you want to measure against.
4. Choose Compare and review Comparison Results.
5. Use Export to Excel when you need the complete comparison workbook.

“Current” in this dialog describes the newer side of the comparison; verify the selected file instead of assuming it is the project’s Current designation. You cannot compare a schedule with itself.

The direction matters. Reversing the files reverses what added/deleted means and how changes are interpreted. Include the two names, IDs, and status dates when explaining the result to someone else.

Compare within the Gantt

Open the schedule you are reviewing, enable Compare, and select the reference schedule. Use the reference display and available comparison columns to inspect differences alongside the current activity.

Add the fields needed for the question, then focus on the affected WBS or milestone. A timeline overlay can quickly show a shifted finish, but use the numerical fields and Details to distinguish date movement from changed duration, actual progress, or constraints.

Turn off Compare when the overlay is no longer needed. Selecting a comparison file does not replace the open working schedule.

Read the differences in a useful order

Start with the important milestone and project-finish changes, then inspect:

1. Added and deleted activities: did scope or activity identity change?
2. Duration changes: is there more or less remaining work, or a revised plan?
3. Logic changes: were relationships added, removed, or changed?
4. Constraints: is a new date restriction holding or forcing work?
5. Other attributes: did calendars, names, classifications, or progress change?

A moved bar tells you the result. It does not by itself identify the cause. Follow the Driving Path and inspect the changed inputs.

Keep activity identity consistent

Comparisons depend on identifying the same work across schedules. Maintain consistent Activity IDs and source identities when importing recurring updates. Changing an activity’s name is different from replacing it with a new identity.

If work appears as deleted and added when you expected a simple change, check how the source activities were recreated or renumbered and review the import mapping. Similar names alone are not a reliable way to prove two rows represent the same activity.

Use the Changes dashboard

Open Dashboard → Changes to review the tagged update sequence or select a two-schedule comparison. Use the change categories and chart/detail interactions to narrow the review.

The update tags and ordering on Files determine the history available here. A missing or incorrectly ordered tag can make a reporting-period comparison misleading. See Prepare the schedule history.

A monthly review routine

Import or preserve the new issue, verify its status date, and compare it with the previous issue. Review milestone movement first, investigate major logic and duration changes, record explanations in comments or review columns, and export the comparison if needed. Make the reviewed file Current and assign its update tag according to the team’s process.