Is it possible to get the estimated time to completion on a periodic basis, say weekly, and recalculate the end dates?

 

For example I have a task starting on day 1 with estimated duration of 20 days. On day 8, the person working on this task gives an estimated time of 15. The task started normally on day 1, it is the duration that has changed. I know I can change the duration but I would have to manually calculate the new total, ie add the etc to the days already worked on the the task to set the new total. It would be easier to enter remaining days =15 and the end date automaticaly be transfered 15 days after today.

 

Thank you all in advance.

 

PS projectlibre is great but where is the documentation? I see a google docs link in the boards but it is dead,