The Claim digger or Schedule Comparison is a widely used tool in P6 to compare between two projects and detect the differences.
One of the main shortage of the Claim Digger or the Schedule Comparison tool is detecting the changes in calendars.
The tool will not detect any revisions in calendars working hours or changing from Project to Global calendar if both have the same description.
Claim Digger will tell us nothing about calendars other than whether the name of the calendar is different.