MSP Task Durations Change when using a Custom Calendar
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MSP Task Durations Change when using a Custom Calendar


Article ID: 206281


Updated On:


Clarity PPM On Premise Clarity PPM SaaS


When using a custom calendar that has workdays being Sunday thru Thursday, the duration changes when exporting a project to MSP. 

Steps to Reproduce:

  1. Create a new calendar having 8 hour workdays between Sunday - Thursday (Friday and Saturdays are non-workdays)
  2. Create a project in Clarity
  3. Export this project to MSP
  4. Change the Project calendar to the new calendar created in Step 1
  5. Create a 5 day duration task with dates starting on Sunday and ending on a Thursday (example: 1/10/2020 - 1/14/2020)
  6. Save the project back to Clarity
  7. Confirm that Clarity also shows the task as having the same dates and a duration of 5 days
  8. Re-export the project to MSP

Expected Results: The task has the same start and finish date, and the duration remains at 5 days.

Actual Results: The task dates have changed, and the duration is now 4 days.


Release : 15.9



This is due to a difference between Clarity and Microsoft Project. Microsoft Project has a concept of project calendars, while Clarity does not. Clarity will always use the site calendar to calculate task duration, which may lead to inconsistencies as described above.


Depending on your requirements, consider any of these workarounds:

  • Assign a dummy assignment
  • Make the task be Fixed Duration

Additional Information

To change this functionality would require an enhancement request. For additional details on the current enhancement process, see: Enhancement Requests for Clarity.