• https://www.linkedin.com/pulse/comparing-working-time-calendars-using-xer-toolkit-schedule-toolkit?trk=prof-post
• 

• It is not an out of the box solution, you must use external software for full calendar comparison if using P6 or MSP; looks better than the other alternatives for MSP and P6, looks easy to use if calendar exceptions are limited. 

• If you use named calendars as it might be in some schedules calendar exceptions can run in the thousands, If the difference is applied to the same day but different hours/minutes/seconds comparing one by one the differences can be a monumental task. By itself it will not report the difference you still got to compare visually and manually look for what the differences are therefore I will give it a 1 out of 5, better than nothing but still a primitive approach. 

• It is easier and less error prone if you can simply filter for changed exceptions and print a report without much effort as you can do with other software such as Spider Project. 
• 

P6 Claim Digger Calendars comparison is primitive. It also look like Schedule Analyzer Calendars - Calendars Definition Report also runs short to identify changes on specific day work hours.  

Say for 7/2/2015 on update the specific days work hours canged from 8 hours to 4 hours as Pepito is on leave on special assignment on 7/2/2015 form work hour 3 to work hour 6. 

P6 database knows Pepito is to be available only 4 hours on 7/2/2015 an otherwise regular work day if not for this exception but neither P6 and most probably Claim Digger will not make it transparent, it is not clear if Claim Digger will disclose the differences. 

www.scheduleanalyzer.com/sa_calendar.htm 

• A funny thing happened when Primavera created P6; they forgot to let you see your calendars and compare them! Claim Digger does not list calendar changes. Schedule Analyzer Enterprise has covertly added this functionality in their Baseline Checker and Update Checker for years. The Schedules utility just makes the entire process transparent and useable.
  • Not sure if fully transparent as claimed !
  • Ron Winter comments would be welcomed.
• There is a problem thought; calendars change their ‘name’ with every update. 

Maybe you can show a Claim Digger report that will disclose the difference of work hours on 7/2/2015. The calendars definition report is still a primitive approach as you will have to compare exceptions day by day among all calendars of the compared schedule versions. 

If using Spider Project:

1. Select Baseline/Comparison Schedule
2. In Gantt select to display a comparison column for assigned calendars. Activities as well as resource calendars will be displayed.
3. In Calendars, Weeks and Calendar Exceptions Tables select to display all comparison columns or choose to display comparison difference. You can create a filter on each table to display only changed rows. With a script you can automate the comparison and export changed lines on all tables into Excel. It would be insane to compare one by one all calendar exceptions by comparing day by day.

If using other software as I recall none will adequately display calendar exceptions so you will have to compare exceptions day by day among all calendars of the compared schedule versions, a primitive approach. No external file comparison software goes into the details of calendar exceptions so you will still miss this comparison unless using Spider Project.

All software needs to keep the calendar exceptions on a table within the database, the information is there within all! Here no rocket science, no sophisticated algorithms needed, just some transparency.

By making changes in calendar exceptions (non-work time) a scheduler can manipulate schedule comparisons in a way very difficult to find out, especially if instead of making a full day as non-work day only a fraction of work hours are changed, say 90% of the original work hours are changed to non-work hours. A smart, not well intentioned scheduler can easily deceive others with the manipulation of calendar exceptions.