Formula to mesasure running time

Markus
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Hi everyone,
I need help on the following topic. I am trying to create a formula to show (measure) the running time in days between the column "done" and the column "creation date"?
(see attached image).
Thanks for your feedback
Comments
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The cell history can not be accessed from the GUI.
You will need to use the API for this. I think some of the automation tools MAY expose this, but I don't think it is intentional and therefore the API may be the only way to do this.
Craig
--Update--
This post triggered a new thought on Zapier:
https://community.smartsheet.com/discussion/capture-start-time-and-finish-time-form