Parent Task Duration appears to not be calculating correct

[MichaelSMN]

We are working through a process of adjusting task duration down to 0 days in the event that a task is marked as not required, essentially streamlining our timeline if a user says certain tasks are not required.  When doing so, a weird thing appears to be happening where the parent task is not reflecting the correct 0 day duration and appears to be holding onto some days for some unknown reason.

Any idea why the parent task would show anything other than 0 days duration in this image (its holding onto 2 days somehow)?

On a second test project, i manually typed out a very similar layout with 1 parent task and 4 sub tasks, i set these all up with a duration >0, then changed them to 0 just to test the same process.   In this example, the parent task is calculating correct with 0 days duration.  

[Madalyn_Destafney]

Without knowing all the nuances of your settings like start time, start mode or completion mode, etc. my best guess is your first example is showing 2 days bc it's child tasks span 2 days - 12.08 start -12.09 completion. Your 2nd example starts and ends 12.23. Check your planned hours column (not shown) as that may be influencing things, you could have planned hrs but still a 0-day duration.

[MichaelSMN · Accepted solution]

Really appreciate the review.  I took a look at the planned hours, and they are all showing 0 hours as well.   

Based on the review of hours like you suggested, I found the issue or what is causing it.  I found a global setting that when an approval is added to a task, to add 1 day to the planned completion date.   When I removed the approval from the test 1 project tasks, the projected duration of the task changed from 1 day down to 0; when I added the approval path back in it added the 1 day duration back to the task.  

Thanks for the help reviewing and hope this might help someone if they come across this challenge as well in the future - check task duration, hours, and global approval setting for potential impact on timeline!