The trick for doing that is a combination of
Custom field that holds the "age" of the project (default to 1/0).
A scheduled workflow rule that runs on the Project that adds 1 day for a project each on a daily basis if it passes the evaluation criteria (e.g. $State<>'Completed' && $State<>'Cancelled').
Regarding the last part I would recommend to use the actual start date. You can populate it by use this app: http://www.clarizen.com/appsmarketplace/item/Set-Actual-Start-Date.html or create a workflow rule that will populate it when for example the project becomes Active/Executable etc and set the date to: OrganizationNow(). In addition, I would recommend to change system setting 10.1 to populate the actual end date to populate upon completion to 'Set to Current Date & Time).
By doing that you can use Clarizen OOTB capability to compare between the plan and the actual timelines.
I would recommend to join one of our Advanced Q&A webinar for further guidelines and recommendations on this use case.